Acoustic noise suppression system, computer-implemented method therefor, computer program and non-volatile data carrier

Abstract

Each device in a set of signal relaying devices (D1, D2, D3) acquires a respective instance (A1s, A2s, A3s) of an acoustic source signal (A) emitted from a noise pollution source (S), produces a respective feedforward signal (s1, s2, s3) comprising the respective instance (A1s, A2s, A3s) together with information designating a respective position (P1, P2, P3) of the device and time-stamp data (t1, t2, t3) to indicate when and where the respective instance (A1s, A2s, A3s) of the acoustic source signal (A) was acquired, and transmits this in a respective radio signal (R1, R2, R3). A target device (T) receives the respective radio signals (R1, R2, R3), and based thereon produces a cancelling signal (CSST) for an anti-noise signal (ANST) that suppresses the acoustic source signal (AT) after having propagated from the noise pollution source (S) to the target device (T). The cancelling signal (CSST) is produced based on the respective instances (A1s, A2s, A3s), the time-stamp data (t1, t2, t3), the information designating the respective positions (P1, P2, P3) of the devices and a target position (PT) of the target device (T).

Description

TECHNICAL FIELD

[0001] The present invention relates generally to suppression of undesired sounds. Especially, the invention relates to a system according to the preamble of claim 1 and a corresponding computer-implemented method. The invention also relates to a computer program for executing the method, and a non-volatile data carrier storing such a computer program.BACKGROUND

[0002] Today, there is a plethora of sounds in almost all environments where people are. The vast majority of these sounds originate from undesired sources, i.e., constitute sound pollution to the subject experiencing them. Of course, the subject may wear ear protection. However, typically, ear protection devices attenuate all kinds of sounds to an equal extent, at least within a defined frequency range. Consequently, it is difficult to distinguish and pass through only those sounds that are relevant to a particular person. The prior art comprises examples of technical solutions that attempt to attain a selective cancellation of undesired sounds.

[0003] US 9,378,753 describes a system for self-organized acoustic signal cancellation over a network. The system may transmit an acoustic sounding signal to an interfering device so that a channel measurement may be performed for a channel between the interfering device and an interferee device. The system may receive the channel measurement for the channel from the interfering device and also receive a digitized version of an audio interference signal associated with the interfering device. Based on the channel measurement and the digital version of the interference signal, the system may calculate a cancellation signal prior to the arrival of the original over-the air audio interference signal that corresponds to the digital version of audio interference signal. The system may then apply the cancellation signal to an audio signal associated with the interferee device to remove the interference signal from the audio signal.

[0004] US 9,704,468 discloses an apparatus and method for cancelling signal noise. According to one embodiment, an apparatus for cancelling signal noise has a sensor or receiver to capture the undesirable signals. A transducer converts the energy of the captured signals and modulates the captured undesirable signals. A signal inverting circuit is connected to the transducer to generate the inverse of the captured undesirable signals by inverting the amplitude of the undesirable signal while maintaining the frequency at the same level. The generated inverse of the undesirable signal transmitted by a transmitter is received by a receiver and output through a speaker so that the output inverse of the undesirable signal is combined with the undesirable signal to produce a desired signal environment.

[0005] WO 2006 / 066618 reveals a speech communication unit that comprises a receiver for receiving a speech and noise signal, a signal processing function operably coupled to the receiver and a noise cancellation function operably coupled to the signal processing function. The speech communication unit receives noise information from a proximal communication unit: and processes the noise information in the signal processing function. The speech communication unit utilizes the processed noise information in the noise cancellation function to cancel out noise from the received speech and noise signal.

[0006] The known solutions, however, leave room for further improvements. For example, insuficcient measures are taken to ensure that the noise-cancelling signals are synchronized with the noise signal to be cancelled at a particular location.SUMMARY

[0007] The object of the present invention is therefore to offer an improved noise-suppression solution that addresses the above problem.

[0008] According to one aspect of the invention, the object is achieved by an acoustic noise suppression system, which includes a set of signal relaying devices and a target device. Each device in the set of signal relaying devices is configured to acquire a respective instance of an acoustic source signal that is emitted from a noise pollution source and produce a respective feedforward signal containing the respective instance of the acoustic source signal. Each of said devices is further configured to transmit a respective radio signal, which includes the respective feedforward signal. The target device is configured to receive the respective radio signals, and based thereon produce a cancelling signal adapted to form a basis for an anti-noise signal, which is estimated to suppress the acoustic source signal after having propagated through a fluid, e.g. air, from the noise pollution source to the target device. Each of the signal relaying devices is further configured to include information, in the device in the respective feedforward signal, which information designates a respective position of the device and time-stamp data indicating when the respective instance of the acoustic source signal was acquired. Here, the time-stamp data refer to a time frame that is common to the signal relaying devices and the target device. Additionally, the target device is configured to produce the cancelling signal on the further basis of the time-stamp data, a target position of the target device and the information that designates the respective positions of the devices in said set.

[0009] This system is advantageous because it enables a highly accurate timing of the cancelling signal in relation to the propagation of the acoustic source signal through the fluid; and as a result, the acoustic source signal may be very efficiently attenuated at the target position.

[0010] According to one embodiment of this aspect of the invention, the target device contains a signal processing unit that is configured to derive an estimated position for the noise pollution source based on the respective positions of the signal relaying devices and the time-stamp data included in the feedforward signals. Based on the derived estimated position for the noise pollution source, in turn, the signal processing unit is configured to determine an estimated time when the acoustic source signal reaches the target position after having propagated through the fluid from the noise pollution source. On the further basis thereof, the signal processing unit in the target device is configured to produce the cancelling signal based on the common time frame, such that the anti-noise signal reaches the target position with a timing that matches the estimated time when the acoustic source signal reaches the target position. Consequently, the sound waves of the acoustic source signal may basically be fully extinguished at the target position.

[0011] Preferably, the set of devices includes at least three signal relaying devices and based on the time-stamp data from the respective signal relaying devices, the signal processing unit in the target device is configured to: (i) calculate a respective distance between each of the respective signal relaying devices and the noise pollution source, and based thereon calculate a distance from a position of the noise pollution source to the target position. This namely facilitates an accurate timing of the cancelling signal.

[0012] According to another embodiment of this aspect of the invention, the signal processing unit in the target device is configured to produce the cancelling signal so that the anti-noise signal contains a stream of soundwaves with such amplitude variations that the anti-noise signal is estimated to cancel out an audible stream of soundwaves comprised in the acoustic source signal at the target position. In other words, at each point in time, the amplitude of the cancelling signal is equal to, however has the opposite sign, of the source signal, and the resulting sound energy therefore becomes zero.

[0013] According to yet another embodiment of this aspect of the invention, the target device is configured to receive repeated updates of the respective radio signals. Based on these updates, in turn, the signal processing unit in the target device is configured to determine, repeatedly, an updated estimated time when the acoustic source signal reaches the target position after having propagated through the fluid from the noise pollution source. On the further basis of said updated determining, said signal processing unit is configured to produce the cancelling signal based on the common time frame, such that the anti-noise signal reaches the target position with a timing that continues to match the updated estimated time when the acoustic source signal reaches the target position. Thus, notwithstanding any movements of the signal source, the signal relaying devices and / or the target device, the cancelling signal may be produced with an adequate timing.

[0014] According to still another embodiment of this aspect of the invention, the devices in the set and the target device are all configured to obtain the common time frame via timing signals that are received from at least one a GNSS (global navigation satellite system), a mobile telephony system and / or a Wi-Fi network. Thus, a reliable and unambiguous time base is provided to all relevant devices.

[0015] According to another embodiment of this aspect of the invention, each of the signal relaying devices is comprised in a portable device in the form of a mobile telephone, a smartphone, a tablet computer and / or a laptop computer. This means that, in practice, most of today's communication devices may be converted into signal a relaying device by installing a software therein, such as a so-called app.

[0016] Preferably, each of the signal relaying devices includes a microphone, i.e. a sound-to-electricity transducer, which is configured to acquire the respective instance of the acoustic source signal emitted from the noise pollution source and convert this signal into an electrical equivalence. Each of the signal relaying devices also includes a first radio interface, which is configured to transmit the respective radio signal to the target device.

[0017] According to a further embodiment of this aspect of the invention, the first radio interface is configured to transmit the respective radio signal directly to the target device via a BLE connection, a Bluetooth connection, an ANT connection, a UWB connection, a Zigbee connection, a Wireless USB connection and / or a Wi-Fi connection. Namely, this allows a shortest possible signal path for the radio signals, which, in turn, translates into minimal latency before the signal is available for processing in the target device.

[0018] Preferably, for the same reasons, the target device includes a second radio interface, which is configured to receive the respective radio signals directly from each of the signal relaying devices via a BLE connection, a Bluetooth connection, an ANT connection, a UWB connection, a Zigbee connection, a Wireless USB connection and / or a Wi-Fi connection.

[0019] According to another embodiment of this aspect of the invention, the target device is included in a portable device in the form of a mobile telephone, a smartphone, a tablet computer, a laptop computer, a digital audio player and a hearing aid device. Thus, most of today's communication devices may be converted into a target device by installing a software therein, such as a so-called app.

[0020] According to still another embodiment of this aspect of the invention, the target device includes at least one output interface, which is configured to be connected via a wire connection or a wireless connection to an earphone unit and / or a headphone unit. Hence, a subject may achieve a noise free experience via his / her standard listening devices. Preferably the wireless connection is here implemented according to any of the standards BLE, Bluetooth, ANT, UWB, Zigbee and / or Wireless USB.

[0021] According to yet another embodiment of this aspect of the invention, each of the signal relaying devices is configured to monitor a signal strength of the acquired respective instance of the acoustic source signal that is emitted from the noise pollution source. If, in a particular signal relaying device, the signal strength subceeds a first threshold level, this device is configured to control itself to a standby mode in which the signal relaying device refrains from producing the respective feedforward signal and transmitting the respective radio signal. If, during a period when the signal relaying device is in the standby mode, the signal strength of the acquired respective instance of the acoustic source signal that is emitted from the noise pollution source exceeds a second threshold level above the first threshold level, the signal relaying device is configured to control itself to an active mode in which the signal relaying device produces the respective feedforward signal and transmits the respective radio signal. Consequently, the signal relaying devices may automatically switch between active operation and standby mode depending on the existence of a nearby acoustic noise source, and thus economize their energy usage. Naturally, as in all mobile devices, this is key to obtain an extended battery life.

[0022] According to another aspect of the invention, the object is achieved by a computer-implemented method for acoustic noise suppression, which method involves the steps of: acquiring, in each device of a set of signal relaying devices, a respective instance of an acoustic source signal that is emitted from a noise pollution source; producing, in each of said devices, a respective feedforward signal containing the respective instance of the acoustic source signal; transmitting, from each of said devices, a respective radio signal containing the respective feedforward signal; receiving in a target device the respective radio signals; and based thereon producing, in the target device, a cancelling signal adapted to form a basis for an anti-noise signal that is estimated to suppress the acoustic source signal after having propagated through a fluid from the noise pollution source to the target device; including, in each of the respective feedforward signals, information designating a respective position of the device and time-stamp data indicating when the respective instance of the acoustic source signal was acquired in the device, which time-stamp data refer to a time frame that is common to the devices in said set and the target device; and producing, in the target device, the cancelling signal on the further basis of the time-stamp data, a target position of the target device and the information designating the respective positions of the devices in said set. The advantages of this method are apparent from the discussion above with reference to the proposed system.

[0023] According to a further aspect of the invention, the object is achieved by a computer program loadable into a non-volatile data carrier communicatively connected to at least one processing unit. The computer program includes software for executing the above method when the program is run on the at least processing unit.

[0024] According to another aspect of the invention, the object is achieved by a non-volatile data carrier containing the above computer program.

[0025] Further advantages, beneficial features and applications of the present invention will be apparent from the following description and the dependent claims.BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The invention is now to be explained more closely by means of preferred embodiments, which are disclosed as examples, and with reference to the attached drawings. Figure 1shows an overview of an acoustic noise suppression system according to one embodiment of the invention; Figures 2a-cshow examples illustrating how an instance of an acoustic signal may be acquired, forwarded and utilized to produce an anti-noise signal according to one embodiment of the invention; Figure 3shows a block diagram of a signal-relaying device according to one embodiment of the invention; Figure 4shows a block diagram of a target device according to one embodiment of the invention; Figure 5illustrates how an earphone unit may be arranged to cancel noise at a target position according to one embodiment of the invention; Figure 6illustrates how the relative positions of the noise source and the target device may be determined and used according to one embodiment of the invention; and Figure 7illustrates, by means of a flow diagram, the general method for acoustic noise suppression according to the invention. DETAILED DESCRIPTION

[0027] Figure 1 shows an overview of an acoustic noise suppression system according to one embodiment of the invention. The scenario here is that there is a noise pollution source S that emits an acoustic source signal A whose audibility to a user U should be minimized.

[0028] The system includes a set of signal relaying devices D1, D2 and D3 respectively and a target device T. Each device D1, D2 and D3 in the set of signal relaying devices is configured to acquire a respective instance A1 s , A2 s and A3 s respectively of the acoustic source signal A. Each of the devices D1, D2 and D3 is further configured to produce a respective feedforward signal s1, s2 and s3 respectively that contains the respective instance A1 s , A2 s and A3 s of the acoustic source signal A and transmit a respective radio signal R1, R2 and R3 respectively that includes the respective feedforward signal s1, s2 and s3.

[0029] Referring now to Figure 3, according to embodiments of the invention, each of the signal relaying devices D1, D2 and D3 includes a respective first radio interface 340 that is configured to transmit the respective radio signal R1, R2 and R3, for example via a BLE (Bluetooth Low Energy) connection, a Bluetooth connection, an ANT (Adaptive Network Topology) connection, a UWB (Ultra-wide-band) connection, a Zigbee connection based on the IEEE (Institute of Electrical and Electronics Engineers) standards specification 802.15, a Wireless USB (Universal Serial Bus) connection and / or a Wi-Fi connection, i.e., based on the IEEE 802.11 family of standards.

[0030] The target device T is configured to receive the respective radio signals R1, R2 and R3 respectively and based thereon produce a cancelling signal CS ST that is adapted to form a basis for an anti-noise signal AN ST . The anti-noise signal AN ST contains a stream of soundwaves with such amplitude variations that the anti-noise signal is estimated to cancel out, or at least suppress significantly, the audible stream of soundwaves comprised in the acoustic source signal A at a target position PT of the target T after that the acoustic source signal AT has propagated through a fluid, such as air, from the noise pollution source S to the target position PT. The cancelation / suppression is accomplished due to that, at the target position PT, the acoustic source signal AT and the anti-noise signal AN ST combine in a destructive manner at each point in time, so that a resulting acoustic energy becomes zero, or at least close to zero.

[0031] Referring to Figure 4 and analogous to the above, according to embodiments of the invention, the target device T contains a second radio interface 430, which is configured to receive the respective radio signals R1, R2 and R3 respectively directly from each of the signal relaying devices D1, D2 and D3 respectively via a BLE connection, a Bluetooth connection, an ANT connection, a UWB connection, a Zigbee connection, a Wireless USB connection and / or a Wi-Fi connection.

[0032] To produce the cancelling signal CS ST , each of the devices D1, D2 and D3 is configured to include in the respective feedforward signal s1, s2 and s3 respectively information designating a respective position P1, P2 and P3 respectively of the device in question and time-stamp data t 1 , t 2 and t 3 that indicates when the respective instance A1 s , A2 s and A3 s of the acoustic source signal A was acquired in the device in question. The time-stamp data refer to a time frame t that is common to all the devices D1, D2 and D3 and the target device T. This will be discussed below, inter alia with reference to Figures 2a to 2c and 6.

[0033] The target device T is configured to produce the cancelling signal CS ST on the further basis of the time-stamp data t 1 , t 2 and t 3 , the target position PT and the information designating the respective positions P1, P2 and P3 respectively of the devices D1, D2 and D3.

[0034] For example, to this aim, the target device T may employ a triangulation strategy. Therefore, the set of signal relaying devices preferably contains at least three devices D1, D2 and D3. Of course, any larger number signal relaying devices is conceivable. However, 3 to 8 is typically sufficient. Figure 6 illustrates how the triangulation strategy may be carried out according to one embodiment of the invention. Here, based on the time-stamp data t 1 , t 2 and t 3 respectively from the respective signal relaying devices D1, D2 and D3, the signal processing unit 410 in the target device T is configured to calculate a respective distance d S1 , d S2 , and dss between each of the respective signal relaying devices D1, D2 and D3 respectively and the noise pollution source S. Since the time-stamp data t 1 , t 2 and t 3 relate to the common time base it is straightforward to calculate the distances d S1 , d S2 and dss. Based thereon, the signal processing unit 410 is further configured to calculate a distance d ST from a position PS of the noise pollution source S to the target position PT. This, in turn, renders it possible to determine a propagation time for the acoustic source signal A from the noise pollution source S to the target position PT. Given that the fluid in which the acoustic source signal A travels is air at room temperature and normal atmospheric pressure, the propagation speed of the acoustic source signal A is approximately 346 meters per second. This is substantially slower that the propagation speed of the radio signals R1, R2 and R3 from the signal relaying devices D1, D2 and D3, which is essentially equal to the speed of light in air, i.e. 299 702 547 meters per second, or a factor over 866 000 times quicker than the propagation speed of the acoustic source signal A. Thus, depending on the specific distances d S1 , d S2 , dss and d ST the signal processing unit 410 will have more or less time at its disposal to produce the cancelling signal CS ST . However, due to the extreme differences in propagation speeds between soundwaves and radio signals, there will always be a temporal space for preparing the cancelling signal CS ST before the acoustic source signal AT arrives at the target position PT provided that the signal relaying devices D1, D2 and D3 are located closer to the noise pollution source S than the target device T.

[0035] To acquire the respective instances A1 s , A2 s and A3 s of the acoustic source signal A1, A2 and A3 respectively emitted from the noise pollution source S, each of the signal relaying devices D1, D2 and D3 includes a respective microphone, i.e. a transducer for converting acoustic signals to electrical ditto. Figure 3 exemplifies this by the reference numeral 330 with respect to the signal relaying devices D1. Preferably, each of the signal relaying devices D1, D2 and D3 also includes a respective sampling unit (not shown), which is configured to convert said electric signal into an equivalent sampled signal, for example on a digital format.

[0036] According to one embodiment of the invention, the first radio interface of each of the signal relaying devices D1, D2 and D3 is configured to transmit the respective radio signals R1, R2 and R3 respectively directly to the target device T. Figure 3 exemplifies this by the reference numeral 340 designating a radio interface in the signal relaying device D1. To minimize the latency before the respective instances A1 s , A2 s and A3 s of the acoustic source signal A1, A2 and A3 are available for processing in the target device T it is important that the radio signals R1, R2 and R3 are transmitted directly from each of the signal relaying devices D1, D2 and D3 to the target device T, i.e., not via a backbone network or similar.

[0037] According to one embodiment of the invention, the signal processing unit 410 in the target device T is specifically configured to derive an estimated position PS for the noise pollution source S based on the respective positions P1, P2 and P3 of the signal relaying devices D1, D2 and D3 respectively and the time-stamp data t 1 , t 2 and t 3 comprised in the feedforward signals s1, s2 and s3 respectively. As described above with reference to Figure 6, the signal processing unit 410 may be configured to derive estimated position PS for the noise pollution source S by employing a triangulation strategy. Based on the estimated position PS, in turn, the signal processing unit 410 is configured to determine a propagation time T P to the target position PT, and thus also an estimated time t T when the acoustic source signal AT reaches the target position P T after having propagated through the fluid from the noise pollution source S. On the further basis thereof, and based on the common time frame t, the signal processing unit 410 is configured to produce the cancelling signal CS ST , such that the anti-noise signal AN ST reaches the target position PT with a timing that matches the estimated time when the acoustic source signal AT reaches the target position PT, i.e., so that the anti-noise signal AN ST may cancel out the acoustic source signal AT at the target position PT as described above.

[0038] Figures 2a to 2c schematically illustrate said cancellation. Figure 2a shows an example of a source signal instance A1 s acquired by the signal relaying device D1 at a point in time t 1 , which instance A1 s is a soundwave that has particular amplitude variations as a function of time t. Figure 2b shows an estimated appearance of this soundwave AT at the point in time t T after having propagated through the fluid to the target position PT. Here, the soundwave's amplitude variations over time t are the same as in Figure 2a, however the magnitudes are smaller due to damping and diffusion of the acoustic energy of the soundwave in the fluid over the distance d ST between the noise pollution source S and the target position PT. Figure 2c shows the anti-noise signal AN ST as a function of time t, which, in each point in time, has the same amplitude as the soundwave AT in Figure 2b, however with the opposite sign. Thus, the anti-noise signal AN ST will cancel out, or at least suppress substantially, the acoustic source signal AT at the target position PT. As a result, the stream of soundwaves comprised in the acoustic source signal AT will not be audible at the target position PT.

[0039] To ensure that the target device T is able to cancel out / suppress the acoustic source signal AT at the target position PT even though one or more of the noise pollution source S, the signal relaying devices D1, D2 and / or D3 and / or the target device T may move over time, the target device T is preferably configured to receive repeated updates of the respective radio signals R1, R2 and R3 respectively, and based thereon, the signal processing unit 410 in the target device T is configured to determine, repeatedly, an updated estimated time t T when the acoustic source signal AT reaches the target position PT after having propagated through the fluid from the noise pollution source S. On the further basis of said updated determining, in turn, the signal processing unit 410 is configured to produce the cancelling signal CS ST based on the common time frame t, such that the anti-noise signal AN ST reaches the target position PT with a timing that matches the updated estimated time t T when the acoustic source signal AT reaches the target-position PT. To enable this, of course, each of the signal relaying devices D1, D2 and D3 must also repeatedly acquire a respective instance A1 s , A2 s and A3 s of the acoustic source signal that is emitted from a noise pollution source S, produce a respective updated feedforward signal s1, s2 and s3 containing the respective instance A1 s , A2 s and A3 s of the acoustic source signal A, and transmit a respective radio signal R1, R2 and R3 that includes the respective feedforward signal s1, s2 and s3 respectively.

[0040] Nevertheless, to conserve energy in the signal relaying devices D1, D2 and D3 and provide an extended battery life for these devices, it is advantageous if the above updating is not performed unnecessarily, for example when no acoustic source signal A is detected by the signal relaying device in question, or if a particular signal relaying device determines that the noise pollution source S is located at such distance from target device T that it is estimated that the acoustic source signal A will not be audible at the target position PT anyway.

[0041] Therefore, according to one embodiment of the invention, each of the signal relaying devices D1, D2 and D3 respectively is configured to monitor a signal strength of the acquired respective instance A1 s , A2 s and A3 s respectively of the acoustic source signal A that is emitted from the noise pollution source S. If the signal strength subceeds a first threshold level, each of the signal relaying devices D1, D2 and D3 respectively is configured to control the signal relaying device D1, D2 and D3 respectively to a standby mode in which the signal relaying device D1, D2 and D3 respectively refrains from producing the respective feedforward signal s1, s2 and s3 respectively and transmitting the respective radio signal R1, R2 and R3 respectively. If, during a period when the signal relaying device D1, D2 and / or D3 respectively is in the standby mode, the signal strength of the acquired respective instance A1 s , A2 s and / or A3 s respectively of the acoustic source signal A that is emitted from the noise pollution source S exceeds a second threshold level above the first threshold level, the signal relaying device D1, D2 and / or D3 respectively that acquired respective instance A1 s , A2 s and / or A3 s in question is configured to control itself to an active mode in which the signal relaying device D1, D2 and / or D3 respectively produces the respective feedforward signal s1, s2 and / or s3 and transmits the respective radio signal R1, R2 and / or R3.

[0042] According to one embodiment of the invention, the signal relaying devices D1, D2 and D3 and the target device T are all configured to obtain the common time frame t via timing signals received from a GNSS, a mobile telephony system and / or a Wi-Fi network. Thus, the signal relaying devices D1, D2 and D3 and the target device T may be embodied in different terminals of a common mobile data communication or telephony system. Nevertheless, one or more of these units may equally well be embodied in units of different systems, however which units obtain the common time frame t via timing signals from the same source, such as a particular GNSS, like GPS (the U.S.-based Global Positioning System, GLONASS (the Russia-based Global Positioning System), BeiDou (BDS, the China-based Global Positioning System) or Galileo (the EU / ESA-based Global Positioning System).

[0043] According to embodiments of the invention, the signal relaying devices D1, D2 and D3 respectively are contained in a portable device in the form of: a mobile telephone, a smartphone, a tablet computer and / or a laptop computer. Analogously, according to embodiments of the invention, the target device T is contained in a portable device in the form of a mobile telephone, a smartphone, a tablet computer, a laptop computer, a digital audio player or a hearing aid device. Thus, most of today's communication devices may be converted into a signal relaying device and / or a target device respectively by installing a software therein, such as a so-called app.

[0044] For convenience and flexibility, the target device T preferably contains at least one output interface, which is configured to be connected via a wire connection or a wireless connection to an earphone unit and / or a headphone unit. Figure 4 generally illustrates such an output interface by the reference numeral 440 and Figure 5 shows an ear Eu of the user U into which ear Eu an earphone unit 500 has been inserted that has a wireless interface 510 configured to be wirelessly connected to the output interface 400 of the target device T. Thus, the earphone unit 500 may receive the cancelling signal CS ST and cancel out, or substantially suppress, the acoustic source signal AT to the user U.

[0045] According to embodiments of the invention, the wireless connection between the target device T and the earphone unit and / or headphone unit is implemented according to the BLE standard, the Bluetooth standard, the ANT standard, the UWB standard, the Zigbee standard and / or the Wireless USB standard.

[0046] The block diagrams of the signal relaying devices and target device illustrated in Figures 3 and 4 respectively show processors 310 and 410 respectively and non-volatile data carriers 320 and 420 respectively.

[0047] It is generally advantageous if the processors 310 and 410 are configured to effect the above procedure in an automatic manner by executing a respective computer program 325 and 425, which is communicatively connected to a respective memory unit 320 and 420, i.e. non-volatile data carrier, storing respective computer program 325 and 425, which, in turn, contains software for making the processors 310 and 410 execute the actions mentioned in this disclosure when the computer program 325 and 425 respectively is run on the processors 310 and 410 respectively.

[0048] To sum up, and with reference to the flow diagram in Figure 7, we will now describe a computer-implemented method according to the invention for acoustic noise suppression, which method is executed by the processor 310 in each of the signal relaying devices D1, D2 and D3.

[0049] A first step 710 checks if an instance of an acoustic source signal has been acquired, which instance represents an acoustic source signal emitted from a noise pollution source. If so, a step 720 follows; and otherwise, the procedure loops back and stays in step 710.

[0050] In step 720, a feedforward signal is produced, which feedforward signal contains the acquired instance of the acoustic source signal. The feedforward signal also contains information designating a position of the signal relaying device and time-stamp data indicating when the instance of the acoustic source signal was acquired in the signal relaying device, where the time-stamp data refer to a time frame that is common to the target device being an intended recipient of the feedforward signal.

[0051] In a step 730 thereafter, a radio signal is transmitted, which radio signal contains the respective feedforward signal, and which radio signal is intended to be received by said target device. Subsequently, the procedure loops back to step 710.

[0052] Figure 8, describes a computer-implemented method according to the invention for acoustic noise suppression, which method is executed by the processor 410 in the target device T.

[0053] A first step 810 checks if a radio signal has been received, which radio signal has been transmitted by a signal relaying device, and which radio signal contains the above-described feedforward signal. If such a radio signal has been received, a step 820 follows; and otherwise, the procedure loops back and satays ins step 810.

[0054] In step 820, a cancelling signal is produced, which cancelling signal is adapted to form a basis for an anti-noise signal that is estimated to suppress the acoustic source signal after having propagated through a fluid from the noise pollution source to the target device. Here, the cancelling signal is produced based on acquired instance of the acoustic source signal, the time-stamp data indicating when the instance of the acoustic source signal was acquired in the signal relaying device, the position of the signal relaying device and time-stamp data obtained in the target device, which time stamp data refer to the time frame that is common to the signal relaying device and the target device and a target position of the target device. Subsequently, the procedure loops back to step 810.

[0055] The process steps described with reference to each of the Figures 7 and 8 may be controlled by means of a programmed processor. Moreover, although the embodiments of the invention described above with reference to the drawings comprise processor and processes performed in at least one processor, the invention thus also extends to computer programs, particularly computer programs on or in a carrier, adapted for putting the invention into practice. The program may be in the form of source code, object code, a code intermediate source and object code such as in partially compiled form, or in any other form suitable for use in the implementation of the process according to the invention. The program may either be a part of an operating system or be a separate application. The carrier may be any entity or device capable of carrying the program.

[0056] For example, the carrier may comprise a storage medium, such as a Flash memory, a ROM (Read Only Memory), for example a DVD (Digital Video / Versatile Disk), a CD (Compact Disc) or a semiconductor ROM, an EPROM (Erasable Programmable Read-Only Memory), an EEPROM (Electrically Erasable Programmable Read-Only Memory), or a magnetic recording medium, for example a floppy disc or hard disc. Further, the carrier may be a transmissible carrier such as an electrical or optical signal which may be conveyed via electrical or optical cable or by radio or by other means. When the program is embodied in a signal, which may be conveyed, directly by a cable or other device or means, the carrier may be constituted by such cable or device or means. Alternatively, the carrier may be an integrated circuit in which the program is embedded, the integrated circuit being adapted for performing, or for use in the performance of, the relevant processes.

[0057] Variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims.

[0058] The term "comprises / comprising" when used in this specification is taken to specify the presence of stated features, integers, steps or components. The term does not preclude the presence or addition of one or more additional elements, features, integers, steps or components or groups thereof. The indefinite article "a" or "an" does not exclude a plurality. In the claims, the word "or" is not to be interpreted as an exclusive or (sometimes referred to as "XOR"). On the contrary, expressions such as "A or B" covers all the cases "A and not B", "B and not A" and "A and B", unless otherwise indicated. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. Any reference signs in the claims should not be construed as limiting the scope.

[0059] It is also to be noted that features from the various embodiments described herein may freely be combined, unless it is explicitly stated that such a combination would be unsuitable.

[0060] The invention is not restricted to the described embodiments in the figures, however, may be varied freely within the scope of the claims. Any subject-matter falling outside the scope of the claims is provided for information purposes, only.

Claims

1. An acoustic noise suppression system, comprising: a set of signal relaying devices (D1, D2, D3), wherein each device in said set is configured to: acquire a respective instance (A1s, A2s, A3s) of an acoustic source signal (A) emitted from a noise pollution source (S), produce a respective feedforward signal (s1, s2, s3) comprising the respective instance (A1s, A2s, A3s) of the acoustic source signal (A), and transmit a respective radio signal (R1, R2, R3) comprising the respective feedforward signal (s1, s2, s3); and a target device (T) configured to: receive the respective radio signals (R1, R2, R3), and based thereon produce a cancelling signal (CSST) adapted to form a basis for an anti-noise signal (ANST) estimated to suppress the acoustic source signal (AT) after having propagated through a fluid from the noise pollution source (S) to the target device (T), characterized in that each device in said set is further configured to include in the respective feedforward signal (s1, s2, s3): information designating a respective position (P1, P2, P3) of the device and time-stamp data (t1, t2, t3) indicating when the respective instance (A1s, A2s, A3s) of the acoustic source signal (A) was acquired in the device, which time-stamp data refer to a time frame (t) that is common to the devices in said set and the target device (T), and the target device (T) is configured to produce the cancelling signal (CSST) on the further basis of the time-stamp data (t1, t2, t3), a target position (PT) of the target device (T) and the information designating the respective positions (P1, P2, P3) of the devices in said set.

2. The system according to claim 1, wherein the target device (T) comprises a signal processing unit (410) that is configured to: derive an estimated position (PS) for the noise pollution source (S) based on the respective positions (P1, P2, P3) of the devices and the time-stamp data (t1, t2, t3) comprised in the feedforward signals (s1, s2, s3), and based on the derived estimated position (PS) for the noise pollution source (S) determine an estimated time (tT) when the acoustic source signal (AT) reaches the target position (PT) after having propagated through the fluid from the noise pollution source (S); and on the further basis thereof produce the cancelling signal (CSST) based on the common time frame (t) such that the anti-noise signal (ANST) reaches the target position (PT) with a timing that matches the estimated time when the acoustic source signal (AT) reaches the target position (PT).

3. The system according to claim 2, wherein said set comprises at least three signal relaying devices (D1, D2, D3) and, based on the time-stamp data (t1, t2, t3) from the respective signal relaying devices (D1, D2, D3), the signal processing unit (410) is configured to: calculate a respective distance (dS1, dS2, dss) between each of the respective signal relaying devices (D1, D2, D3) and the noise pollution source (S), and based thereon calculate a distance (dST) from a position (PS) of the noise pollution source (S) to the target position (PT).

4. The system according to any one of claims 2 or 3, wherein the signal processing unit (410) is configured to produce the cancelling signal (CSST) so that the anti-noise signal (ANST) comprises a stream of soundwaves with such amplitude variations that the anti-noise signal (ANST) is estimated to cancel out an audible stream of soundwaves comprised in the acoustic source signal (AT) at the target position (PT).

5. The system according to any one of claims 2 to 4, wherein the target device (T) is configured to receive repeated updates of the respective radio signals (R1, R2, R3), and based thereon, the signal processing unit (410) is configured to: determine, repeatedly, an updated estimated time (tT) when the acoustic source signal (AT) reaches the target position (PT) after having propagated through the fluid from the noise pollution source (S); and on the further basis of the updated determining produce the cancelling signal (CSST) based on the common time frame (t) such that the anti-noise signal (ANST) reaches the target position (PT) with a timing that matches the updated estimated time (tT) when the acoustic source signal (AT) reaches the target- position (PT).

6. The system according to any one of the preceding claims, wherein the devices (D1, D2, D3) in said set and the target device (T) are configured to obtain the common time frame (t) via timing signals received from at least one of: a GNSS, a mobile telephony system and a Wi-Fi network.

7. The system according to any one of the preceding claims, wherein the signal relaying devices (D1, D2, D3) are comprised in a portable device in the form of at least one of: a mobile telephone, a smartphone, a tablet computer and a laptop computer.

8. The system according to any one of the preceding claims, wherein each of the signal relaying devices (D1, D2, D3) comprises: a microphone (330) configured to acquire the respective instance (A1s) of the acoustic source signal (A1) emitted from the noise pollution source (S), and a first radio interface (340) configured to transmit the respective radio signal (R1) to the target device (T).

9. The system according to claim 8, wherein the first radio interface (340) is configured to transmit the respective radio signal (R1) directly to the target device (T) via at least one of: a BLE connection, a Bluetooth connection, an ANT connection, a UWB connection, a Zigbee connection, a Wireless USB connection and a Wi-Fi connection.

10. The system according to any of claims 8 or 9, wherein the target device (T) comprises a second radio interface (430) configured to receive the respective radio signals (R1, R2, R3) directly from each of the signal relaying devices (D1, D2, D3) via at least one of: a BLE connection, a Bluetooth connection, an ANT connection, a UWB connection, a Zigbee connection, a Wireless USB connection and a Wi-Fi connection.

11. The system according to any one of the preceding claims, wherein the target device (T) is comprised in portable device in the form of at least one of: a mobile telephone, a smartphone, a tablet computer, a laptop computer, a digital audio player and a hearing aid device.

12. The system according to any one of the preceding claims, wherein the target device (T) comprises at least one output interface (440) configured to be connected via a wire connection or a wireless connection to at least one of an earphone unit (500) and a headphone unit.

13. The system according to claim 12, wherein the wireless connection is implemented according to at least one of the standards BLE, Bluetooth, ANT, UWB, Zigbee and Wireless USB.

14. The system according to any one of the preceding claims, wherein each of the signal relaying devices (D1, D2, D3) is configured to: monitor a signal strength of the acquired respective instance (A1s, A2s, A3s) of the acoustic source signal (A) that is emitted from the noise pollution source (S), and if the signal strength subceeds a first threshold level, control the signal relaying device (D1, D2, D3) to a standby mode in which the signal relaying device (D1, D2, D3) refrains from producing the respective feedforward signal (s1, s2, s3) and transmitting the respective radio signal (R1, R2, R3); and if, during a period when the signal relaying device (D1, D2, D3) is in the standby mode, the signal strength of the acquired respective instance (A1s, A2s, A3s) of the acoustic source signal (A) that is emitted from the noise pollution source (S) exceeds a second threshold level above the first threshold level, control the signal relaying device (D1, D2, D3) to an active mode in which the signal relaying device (D1, D2, D3) produces the respective feedforward signal (s1, s2, s3) and transmits the respective radio signal (R1, R2, R3).

15. A computer-implemented method for acoustic noise suppression, which method comprises: acquiring, in each device of a set of signal relaying devices (D1, D2, D3), a respective instance (A1s, A2s, A3s) of an acoustic source signal (A) emitted from a noise pollution source (S), producing, in each of said devices, a respective feedforward signal (s1, s2, s3) comprising the respective instance (A1s, A2s, A3s) of the acoustic source signal (A), transmitting, from each of said devices, a respective radio signal (R1, R2, R3) comprising the respective feedforward signal (s1, s2, s3), receiving in a target device (T) the respective radio signals (R1, R2, R3), and based thereon producing, in the target device (T), a cancelling signal (CSST) adapted to form a basis for an anti-noise signal (ANST) that is estimated to suppress the acoustic source signal (AT) after having propagated through a fluid from the noise pollution source (S) to the target device (T), characterized by including, in each of the respective feedforward signals (s1, s2, s3), information designating a respective position (P1, P2, P3) of the device and time-stamp data (t1, t2, t3) indicating when the respective instance (A1s, A2s, A3s) of the acoustic source signal (A) was acquired in the device, which time-stamp data refer to a time frame (t) that is common to the devices in said set and the target device (T), and producing, in the target device (T), the cancelling signal (CSST) on the further basis of the time-stamp data (t1, t2, ts), a target position (PT) of the target device (T) and the information designating the respective positions (P1, P2, P3) of the devices in said set.

16. A computer program (325, 425) loadable into a non-volatile data carrier (320, 420) communicatively connected to a processor (310, 410), the computer program (325, 425) comprising software for executing the method according to claim 15 when the computer program (325, 425) is run on the processor (310, 410).

17. A non-volatile data carrier (320, 420) containing the computer program (325, 425) of claim 16.

Images