Acoustic sound emission device

Abstract

Provided is an open-ear acoustic sound emission device capable of more effectively performing ANC on noise or the like in a wider frequency band than in the prior art. This acoustic sound emission device comprises: a silencing speaker; a speaker support part that supports the silencing speaker; a reference microphone; a microphone support part that supports the reference microphone; and a noise cancellation device that generates a silencing signal using an acoustic signal picked up by the reference microphone. The acoustic sound emission device is configured such that a user can hear a direct sound of the acoustic signal coming externally when wearing the acoustic sound emission device, the silencing speaker reproduces the silencing signal, and the microphone support part is connected to the speaker support part, and protrudes in a direction sensitive to the human auditory characteristics with respect to the speaker support part such that the reference microphone is disposed in the sensitive direction.

Description

Acoustic sound playback device

[0001] The present invention relates to a wearable acoustic sound playback device and a technique for eliminating external noise and the like.

[0002] Wearable acoustic sound playback devices include devices that prevent the user from directly hearing the direct sound of an acoustic signal coming from the outside when worn, and devices that allow the direct sound to be heard (hereinafter also referred to as "open-ear type acoustic sound playback devices"). For example, open-ear type earphones that do not block the ear canal, and open-ear type headphones in which the internal space formed by the ear pads and the housing is spatially connected to the external space can hear the direct sound and correspond to open-ear type acoustic sound playback devices. On the other hand, canal type earphones that block the ear canal, and closed-type headphones that cover the entire ear with ear pads and a housing and whose internal space and external space are not spatially connected cannot hear the direct sound and do not correspond to open-ear type acoustic sound playback devices.

[0003] Here, in the case of a wearable acoustic sound playback device, it is often used in a state where noise exists in the surroundings, and in order to make it easier to hear the desired reproduced sound, active noise control (ANC) may be performed.

[0004] Non-Patent Document 1 is known as a prior art of ANC.

[0005] By Kaji Kayan, "Recent Trends in Active Noise Control", Institute of Electronics, Information and Communication Engineers Fundamentals Review, Vol. 17, No. 1, 2023, pp. 36-43.

[0006] FIG. 1 shows an example of the attenuation amount of noise and noise (hereinafter also referred to as "noise etc.") when passive noise cancellation (PNC), active noise cancellation (ANC), PNC, and ANC are combined (see Reference 1).

[0007] (Reference 1) Roschmann-Foudhaili, Hatem, "Semi-Open ANC Headphone", AES Conf., 2016. In PNC, sound-absorbing materials and sound-insulating walls are used to physically prevent surrounding noise from reaching the ear. On the other hand, ANC uses digital signal processing to generate and play a signal (hereinafter also called a "noise-canceling signal") that is in the opposite phase to the sound signal to be canceled out, thereby canceling out the noise. As can be seen from Figure 1, the attenuation by ANC is large in the low frequency range, and the attenuation by PNC is large in the high frequency range, and by combining these, noise can be reduced over a wide frequency range.

[0008] However, in the case of open-ear acoustic devices, there is virtually no sound insulation provided by the structure of the device, so noise of any frequency band reaches the ear.

[0009] The present invention aims to provide an open-ear type acoustic noise emission device that can perform ANC more effectively against noise and other sounds across a wider frequency range than conventional devices.

[0010] To solve the above problems, according to one aspect of the present invention, the acoustic sound emission device is worn by the user. The acoustic sound emission device includes a sound-canceling speaker, a speaker support part that supports the sound-canceling speaker, a reference microphone, a microphone support part that supports the reference microphone, and a noise cancellation device that generates a sound-canceling signal using the acoustic signal picked up by the reference microphone. When the acoustic sound emission device is worn, the user can hear the direct sound of an acoustic signal coming from the outside, the sound-canceling speaker reproduces the sound-canceling signal, and the microphone support part is connected to the speaker support part and is configured to protrude in a direction relative to the speaker support part such that the reference microphone is positioned in a direction that is sensitive to human hearing characteristics.

[0011] According to the present invention, an open-ear type acoustic sound emission device can perform ANC (Active Noise Cancellation) even for noises of 1 kHz or higher.

[0012] A diagram showing examples of noise attenuation for PNC, ANC, and combinations thereof. A diagram explaining the placement of the reference microphone. A diagram explaining the relationship between noise suppression and frequency domain. A functional block diagram of the acoustic sound emission device 100 according to the first embodiment. A side view explaining the appearance of the acoustic sound emission device 100 according to the first embodiment. A front view explaining the appearance of the acoustic sound emission device 100 according to the first embodiment. A functional block diagram of the noise cancellation device 105. A diagram showing an example of the processing flow of the noise cancellation device 105. A diagram explaining the sound reduction performance of the acoustic sound emission device according to this embodiment. A diagram explaining the experimental content. A diagram showing an example of the length of the microphone support. A diagram showing experimental results of noise suppression for each frequency. A diagram showing experimental results of coherence for each frequency. A side view explaining the appearance of the acoustic sound emission device 100, which targets high-frequency noise coming from noise sources on the front and rear sides. A diagram explaining the sound reduction performance of the acoustic sound emission device in Figure 14. A diagram showing an example of the shape of the microphone support 114. A diagram showing an example of the shape of the microphone support 114. A diagram showing an example of the shape of the microphone support part 114. A diagram showing an example of the shape of the microphone support part 114. A diagram illustrating the appearance of the acoustic sound emission device 200 according to the second embodiment.

[0013] Embodiments of the present invention will be described below. In the drawings used in the following description, components with the same function or steps that perform the same processing will be denoted by the same reference numerals, and redundant explanations will be omitted.

[0014] <Key Points of the First Embodiment> In order to cancel high-frequency noise and the like using feedforward ANC, it is important to have a reference microphone placement that satisfies causal constraints.

[0015] Figure 2 is a diagram illustrating the arrangement of the reference microphone. Let Dp be the acoustic delay of the path from the noise source 91 (primary source) to the error microphone 92 (first-order path), Ds be the acoustic delay of the path from the silencer speaker 93 (secondary source) to the error microphone 92 (second-order path), Dr be the acoustic delay of the path from the noise source 91 (primary source) to the reference microphone 94 (reference path), and Dc be the processing delay in the noise cancellation unit 95. In order to satisfy the causality constraint, Dp - Dr > Ds + Dc (1) must be satisfied. Here, the processing delay Dc may include not only the processing delay that occurs when generating the silencer signal from the observed signal, but also electrical delays, mechanical delays that occur in the error microphone 92, silencer speaker 93, and reference microphone 94, as well as processing delays that occur in AD conversion and DA conversion. The acoustic delays Dp and Dr change depending on the position of the noise source 91.

[0016] For example, in the arrangement of the reference microphone 94, error microphone 92, and noise-canceling speaker 93 in headphones as shown in Figure 2, the distance between the reference microphone 94 and the error microphone 92 in the direction of the noise source (when the noise source 91 is in front of the user) is about 4 cm, resulting in Dp-Dr ≈ 0.15 [ms] and Ds ≈ 0.05 [ms]. In typical products, the processing delay Dc is 0.1 [ms] or more for digital signal processors (DSPs), microphones, and speakers.

[0017] The effect of delay is stronger the shorter the wavelength (higher frequency band). Therefore, as the acoustic delays Dr and Ds and processing delay Dc increase, the sound cancellation performance in the high-frequency band tends to deteriorate.

[0018] Figure 3 illustrates the relationship between noise suppression and the frequency domain. As can be seen from Figure 3, when Dr+Ds+Dc is greater than Dp, the noise suppression performance deteriorates significantly in the high-frequency range (e.g., above 1 kHz). In other words, in order to suppress noise in the high-frequency range (e.g., above 1 kHz) in ANC, the causal constraint must be satisfied, that is, Dp > Dr+Ds+Dc (1'), or even if the causal constraint is not satisfied, Dr+Ds+Dc should be brought as close to Dp as possible. Therefore, Dr, Ds, and Dc should be made smaller.

[0019] In this embodiment, we propose a hardware design to reduce the acoustic delay Dr of the reference microphone.

[0020] (Point 1) Noise sources in the midline, especially those coming from the front, can be suppressed not only in the low and mid-range but also in the high-frequency band (e.g., 1 kHz and above). This is because noise reduction against noise coming from the front is considered particularly important for the following reasons.

[0021] (i) Due to the binaural loudness summing effect, even at the same sound pressure level, noise coming from the front is perceived as being approximately 3 dB louder than noise coming from the left or right. Therefore, by suppressing noise coming from the front, even with the same amount of suppression, the user will perceive the noise as being suppressed more effectively.

[0022] (ii) When noise or other sounds are coming from the same direction as the object of attention, it can lead to decreased concentration and increased discomfort. Since people tend to face their faces directly toward the object of attention, suppressing noise or other sounds coming from the front effectively prevents decreased concentration and increased discomfort.

[0023] Note that the forward direction is just one example of a direction in which human hearing is sensitive; any other direction in which human hearing is sensitive may also be used.

[0024] (Point 2) In order to effectively suppress noise sources in the midline, especially high-frequency noise (e.g., 1 kHz or higher) coming from the front, the reference microphone is positioned in a structure that protrudes toward the front of the face. With this configuration, a reference signal with a small acoustic delay Dr can be obtained for noise coming from the front.

[0025] For example, in the case of open-ear headphones, a microphone support is formed on the front side of the housing that covers the baffle to which the driver unit, which functions as a sound-canceling speaker, is attached. This support protrudes forward to the nose, and a reference microphone is attached to the front side of the microphone support. Such microphone support and reference microphone are provided on both the left and right housings.

[0026] In this reference microphone configuration, if the microphone support protrudes forward to a degree that satisfies the causality constraint, it becomes unnecessary to predict future signals based on the position of the error microphone.

[0027] Furthermore, even if the causal constraint is not met, observation signals including noise can be acquired earlier compared to cases where the microphone does not protrude in the forward direction, making it easier to predict future signals based on the position of the error microphone.

[0028] As a result, noise cancellation becomes possible even in the frequency band of 1 kHz or higher in front of the device, and noise cancellation performance is improved in the frequency band of 1 kHz or lower.

[0029] <Acoustic sound emission device 100 according to the first embodiment> Figure 4 shows a functional block diagram of the acoustic sound emission device 100 according to the first embodiment.

[0030] The acoustic sound emission device 100 includes a reference microphone 104, a microphone support 114, a sound-dampening speaker 103, a speaker support 113, an error microphone 102, and a noise cancellation device 105.

[0031] Figures 5 and 6 are a side view and a front view, respectively, illustrating the external appearance of the acoustic sound emission device 100 according to the first embodiment. The acoustic sound emission device 100 is an open-ear type headphone and includes a headband, housing 110, ear pads, etc., with the two left and right housings 110 connected via a hairband.

[0032] The housing 110 includes a first member 111, a microphone support portion 114, a connecting portion 115, and a speaker support portion 113.

[0033] The first component 111 has a hollow cylindrical shape, with ear pads positioned on the surface facing the user. When the user wears the acoustic sound emission device 100, the auricle is retracted into the hollow cylindrical shape. A microphone support portion 114 is also formed on the curved surface of the first component 111 facing the user.

[0034] The microphone support portion 114 is formed to protrude to an extent that it does not extend beyond the nose in the forward direction, and the reference microphone 104 is positioned on the front side of the microphone support portion 114. With this configuration, the reference microphone 104 is positioned in front of the user. The microphone support portion 114 is connected to the speaker support portion 113 via the first member 111 and the connecting portion 115. If the radius of the hollow cylindrical shape of the first member 111 is made extremely large, the reference microphone 104 can be positioned in front of the user even if the reference microphone 104 is placed on the curved surface of the first member 111 without providing the protruding microphone support portion 114. However, in such a configuration, a large portion of the side of the user's head would be covered by the housing 110, resulting in poor comfort. In addition, the sound emission device 100 itself would become large and inconvenient to carry. In this embodiment, by providing the protruding microphone support portion 114, a compact size is achieved while maintaining comfort.

[0035] The speaker support section 113 is roughly cylindrical in shape and is formed to cover the baffle to which the sound-dampening speaker 103 and error microphone 102 are attached. The sound-dampening speaker 103 and error microphone 102 are positioned facing the side opposite the user. In the example shown in Figures 5 and 6, the sound-dampening speaker 103 and error microphone 102 are positioned near the center of the side facing the user. With this configuration, the sound-dampening speaker 103 and error microphone 102 are positioned close to the user's ears.

[0036] <Noise Cancelling Device 105> The noise cancelling device 105 takes the reference signal r(n) picked up by the reference microphone 104 and the error signal e(n) picked up by the error microphone 102 as input, generates a noise cancellation signal y(n) using the reference signal r(n), and outputs it to the noise cancellation speaker 103. Here, n is an index representing time.

[0037] The noise cancellation device 105 is a special device configured by loading a special program into a known or dedicated computer having, for example, a central processing unit (CPU) and main memory (RAM). The noise cancellation device 105 executes each process under the control of, for example, the central processing unit. Data input to the noise cancellation device 105 and data obtained in each process are stored in, for example, main memory, and the data stored in main memory is read to the central processing unit as needed and used for other processes. Each processing unit of the noise cancellation device 105 may be composed of hardware such as integrated circuits, at least in part. Each storage unit of the noise cancellation device 105 can be composed of, for example, main memory such as RAM (Random Access Memory), or middleware such as a relational database or key-value store. However, each storage unit does not necessarily have to be located inside the noise cancellation device 105; it may be composed of auxiliary storage devices made of semiconductor memory elements such as hard disks, optical disks, or flash memory, and may be located outside the noise cancellation device 105.

[0038] The noise cancellation device 105 can be realized using various noise cancellation technologies. For example, it can be realized using the noise cancellation technology described in Non-Patent Document 1.

[0039] An example of implementing feedforward type ANC will be explained. Figure 7 shows a functional block diagram of the noise cancellation device 105, and Figure 8 shows its processing flow.

[0040] The noise canceling device 105 includes an adaptive filtering unit 105-1, a secondary path model unit 105-2, and a filter update unit 105-3. Note that the reference microphone 104 and the error microphone 102 may each include a preamplifier and an AD conversion unit. Also, the noise canceling speaker 103 may include a power amplifier and a DA conversion unit. The preamplifier, AD conversion unit, power amplifier, and DA conversion unit may be configured as components included in the noise canceling device 105.

[0041] The reference microphone 104 picks up the noise emitted from the noise source and arriving through the reference path (S11), and outputs a reference signal r(n).

[0042] <Adaptive Filtering Unit 105-1> The adaptive filtering unit 105-1 takes the reference signal r(n) as an input, filters the reference signal r(n) with a noise control filter, generates a pseudo-noise (cancellation signal y(n)) (S13), and outputs it to the noise canceling speaker 103. The noise canceling speaker 103 reproduces the cancellation signal y(n) (S15) to cancel the noise and the like. The pseudo-noise (cancellation signal y(n)) is generated from the reference signal r(n) using a noise control filter so as to be a signal with the same amplitude and opposite phase with respect to the noise and the like at the location of the error microphone 102.

[0043] The error microphone 102 picks up the remaining sound as a result of the cancellation (S17) and outputs an error signal e(n).

[0044] <Secondary Path Model Unit 105-2> The secondary path model unit 105-2 takes the reference signal r(n) as an input, filters it with a digital filter that models the secondary path (S19), generates a filtered reference signal r’(n), and outputs it.

[0045] <Filter Update Unit 105-3> The filter update unit 105-3 takes the filtered reference signal r’(n) and the error signal e(n) as inputs, updates the filter coefficients of the noise control filter by an adaptive algorithm so as to minimize the error signal (S21), and outputs it. The adaptive filtering unit 105-1 performs processing using the updated noise control filter.

[0046] In addition, in this embodiment, filtering is performed using an adaptive filter, but filtering may be performed using a fixed filter to realize ANC. In that case, the noise canceling device 105 may include a fixed filtering unit instead of the adaptive filtering unit 105-1, and it is not necessary to provide the secondary path model unit 105-2 and the filter update unit 105-3. The fixed filtering unit takes the reference signal r(n) as an input, filters the reference signal r(n) with a noise control filter (fixed filter), generates a pseudo-noise (cancellation signal y(n)), and outputs it to the noise cancellation speaker 103. This noise canceling device 105 is also an example, and it may be realized by various other noise canceling technologies.

[0047] <Effect> With such a configuration, even in the case of an open-ear type acoustic sound emitting device, effective ANC can be performed against noise etc. of 1 kHz or higher, and the noise cancellation performance is also improved against noise etc. of 1 kHz or higher.

[0048] FIG. 9 is a diagram for explaining the noise cancellation performance of the acoustic sound emitting device according to this embodiment. As shown in (A) of FIG. 9, in the front direction of the user of the matte part A, since the microphone support part 114 protrudes and the reference microphone 104 is attached to the tip thereof, the causality constraint is satisfied and the noise cancellation performance is high in a wide frequency band (100 - 4 kHz). On the other hand, in a direction other than the front of the user of the horizontal stripe part B, since the causality constraint is not satisfied, the noise cancellation performance is the same as in the prior art, and the noise cancellation performance is high only in a low frequency band (100 - 1 kHz), and the noise cancellation performance is low in a high frequency band (1 - 4 kHz).

[0049] The acoustic sound emitting device 100 of this embodiment includes two left and right housings 110 for both ears, but it may be configured to include one left or right housing 110 for one ear, and the same effect can be obtained in one ear (see (B) of FIG. 9). However, since noise is still a concern in the ear where noise cancellation is not performed, a configuration including two left and right housings 110 for both ears is more effective.

[0050] <Experimental Results> The experimental results showing the effects of this embodiment will be described.

[0051] Figure 10 is a diagram illustrating the experimental procedure.

[0052] The noise source 91 (speaker) emits pink noise, and the sound-canceling speaker 103 (secondary sound source) is the speaker of an existing open-ear type headphone. In this experiment, the sound emission device 100 is configured to include a housing 110 for the left ear and is attached to a dummy head. The distance between the noise source 91 and the dummy head is 1m.

[0053] The ANC algorithm is a feedforward type ANC based on the time-domain FxLMS algorithm. There is one reference microphone and one error microphone. Figure 11 shows examples of microphone support lengths, with the microphone support lengths being 0 mm (as in conventional technology, the reference microphone is built into the housing), approximately 6 mm, approximately 1.6 mm, approximately 2.6 mm, approximately 3.6 mm, and approximately 4.7 mm, corresponding to (A) to (F) in Figure 11, respectively.

[0054] Broadband noise emitted from a speaker (noise source) and output from an ANC device equipped with a DSP is picked up by an error microphone and a reference microphone connected to the ANC device, and the adaptive filter of the ANC device is learned.

[0055] This trained filter approximates the impulse response of the acoustic path from the speaker (noise source) to the error microphone.

[0056] The impulse response is measured from the noise source to the reference microphone and error microphone, and from the secondary sound source to the reference microphone and error microphone.

[0057] All reference and error microphones used are 4mm diameter electric condenser microphones (ECMs).

[0058] The following explains the evaluation metrics for ANC.

[0059] For both cases where ANC is applied and where it is not, an observed signal including noise (primary source) and pseudo-noise (a cancellation signal, which is a secondary source) is calculated by simulation, converted into a time-frequency domain signal using a short-time Fourien transform (STFT), and the above processes S11 to S21 are repeated.

[0060] In the section where the ANC noise control filter has sufficiently converged and noise reduction is achieved, the average value of the difference L(f) in the logarithmic power spectrum is calculated. A larger difference L(f) indicates higher noise suppression performance at frequency f.

[0061] Figure 12 shows the experimental results for noise suppression at each frequency, and Figure 13 shows the experimental results for coherence at each frequency. However, ref_0 to ref_5 correspond to (A) to (F) in Figure 11, respectively.

[0062] Figure 12 shows that when the microphone support portion 114 protrudes forward from the outer edge of the housing 110 (headphone housing) and a reference microphone 104 is attached to its tip (ref_1 to 5), the sound cancellation performance is higher than when the reference microphone 104 is attached to the outer edge of the housing 110 (headphone housing) (ref_0). Furthermore, at 3kHz and below, it can be seen that the longer the microphone support portion 114 is (i.e., the smaller the acoustic delay Dr of the reference microphone 104), the higher the sound cancellation performance.

[0063] At 3-4kHz, performance degrades if the microphone support section 114 is too long. This is thought to be because the reference microphone 104 and the error microphone 103 are located far apart, resulting in poor coherence between the observed signal from the reference microphone 104 and the observed signal from the error microphone 103 (see Figure 13).

[0064] <Modification> In the first embodiment, it is assumed that noises coming from the front direction will be suppressed, taking into account the binaural loudness summing effect. Also, since people often turn their faces forward towards the direction of the object of attention, if the direction from which the noise is coming and the direction of the object of attention are the same, it will reduce concentration on work and increase discomfort, so it is assumed that noises coming from the front direction will be suppressed. However, the object of suppression in the present invention is not necessarily limited to noises coming from the front direction. If noises coming from a direction to which humans are particularly sensitive in terms of auditory characteristics are made the object of suppression, and the microphone support part 114 is formed to protrude in that direction, and the reference microphone 104 is placed at the end of the microphone support part 114, high-frequency noises coming from that direction can be effectively suppressed. For example, one can imagine a situation where a person is doing desk work using a PC on a bullet train or airplane, and noises are coming from the direction of the PC = in front of the user.

[0065] In the first embodiment, the target of suppression was high-frequency noise arriving from noise sources in the midline, particularly from the front side. However, high-frequency noise arriving from noise sources on the rear side may also be targeted for suppression. Figure 14 is a side view illustrating the appearance of the sound emission device 100, which targets high-frequency noise arriving from both front and rear noise sources.

[0066] The microphone support portion 114 is formed to protrude forward to the extent that it does not extend beyond the nose, similar to the first embodiment, and the reference microphone 104 is positioned on the front side of the microphone support portion 114. Furthermore, the microphone support portion 114 is formed to protrude in the rear direction, and the reference microphone 104 is positioned on the rear side of the microphone support portion 114. The two microphone support portions 114 are connected to the speaker support portion 113 via the first member 111 and the connecting portion 115, respectively.

[0067] Figure 15 is a diagram illustrating the sound silencing performance of the acoustic sound emission device shown in Figure 14. In the textured section A, the microphone support 114 protrudes in the direction in front of and behind the user, and the reference microphone 104 is attached to its tip. This satisfies the causal constraint, resulting in high sound silencing performance over a wide frequency range (100 to 4 kHz). On the other hand, in the horizontal striped section B, the causal constraint is not satisfied in directions other than in front of the user. Therefore, the sound silencing performance is the same as that of the conventional technology, with high sound silencing performance only in the low frequency range (100 to 1 kHz) and low sound silencing performance in the high frequency range (1 to 4 kHz).

[0068] Furthermore, in the first embodiment, the microphone support portion 114 is formed to protrude straight forward, and the reference microphone 104 is positioned on the front side of the microphone support portion 114. However, it is not necessarily required to be formed to protrude straight forward; for example, as shown in Figure 16, it may be formed to protrude forward in an L-shape, and the reference microphone 104 may be positioned on the front side of its end.

[0069] In Figures 5, 6, 14, and 16, the microphone support portion 114 is formed on the lower side with respect to the center of the housing 110, but it may also be formed in the center (see Figure 17) or on the upper side (see Figure 18). In particular, by forming the microphone support portion 114 so that the reference microphone 104 is positioned in front of the user and above the user's eyes (see Figure 18), the impact on vision can be reduced. However, as long as it is in front of the user and not in the user's field of vision when wearing the acoustic device 100, the impact on vision can be similarly reduced by forming the microphone support portion 114 so that the reference microphone 104 is positioned at a location other than above the user's eyes, for example, below.

[0070] Depending on the direction of the suppression target (the direction in which human hearing is particularly sensitive, or the direction from which noise etc. is coming, in other words, the direction of the noise source 91), the microphone support portion 114 may be formed to protrude in that direction (for example, upward, backward), and the reference microphone 104 may be placed at the end in that direction. Alternatively, the microphone support portion 114 may be formed so that the position and direction of the reference microphone 104 are variable. In addition to the reference microphone 104, the microphone support portion 114 may also be equipped with a front-facing camera, a biosignal sensor, etc. Furthermore, when making a call using the acoustic sound emission device 100, the reference microphone 104 may be used as a boom microphone for the call. Moreover, the reference microphone 104 may be configured to be retractable when ANC is not being performed.

[0071] In this embodiment, the headband passes over the top of the head and connects the two left and right housings 110. However, as shown in Figure 19, the headband may be configured to pass around the head and connect the two left and right housings 110. In this case, the headband corresponds to the microphone support portion 114. With this configuration, the microphone support portion 114 is formed to protrude forward to the extent that it does not extend beyond the nose, as in the first embodiment, and the reference microphone 104 is positioned on the front side of the microphone support portion 114. With this configuration, the reference microphone 104 is positioned in front of the user. The microphone support portion 114 is connected to the speaker support portion 113 via the connection portion 115. Note that even in the structure where the headband passes over the top of the head and connects the two left and right housings 110, high-frequency noises coming from a noise source on the rear side may also be targeted for suppression. In this case, since the microphone support portion 114 is also formed to protrude in the rear direction, the reference microphone 104 can be positioned on the rear side of the microphone support portion 114.

[0072] <Second Embodiment> This section will focus on the differences from the first embodiment.

[0073] In the first embodiment, the sound emission device 100 is an open-ear type headphone, but in this embodiment, the sound emission device 200 is an open-ear type earphone.

[0074] The acoustic sound emission device 200 includes reference microphones 204F, 204R, microphone support sections 214F, 214R, a sound-dampening speaker, a speaker support section 213, an error microphone, and a noise cancellation device.

[0075] Figure 20 is a diagram illustrating the external appearance of the acoustic sound emission device 200 according to the second embodiment. The acoustic sound emission device 200 is an open-ear type earphone and includes an ear hook 220, a housing 210, etc., and the two left and right housings 210 are connected by a cable. Figure 20 illustrates the earphone for the right ear.

[0076] The housing 210 includes a speaker support portion 213 and a microphone support portion 214F.

[0077] The speaker support section 213 is columnar in shape, and a hole is provided on its bottom surface facing the user for sound emitted by the sound-dampening speaker to pass through. In addition, a microphone support section 214F is formed on the user-facing side of the speaker support section 213.

[0078] The microphone support portion 214F is formed to protrude forward to an extent that it does not extend beyond the nose, and the reference microphone 204F is positioned on the front side of the microphone support portion 214F. With this configuration, the reference microphone 204F is positioned in front of the user. The microphone support portion 214F is connected to the speaker support portion 213.

[0079] The speaker support section 113 is columnar in shape and is formed to cover a baffle to which a sound-dampening speaker and error microphone (not shown) are attached. The sound-dampening speaker and error microphone are positioned on the bottom surface facing the user. With this configuration, the sound-dampening speaker and error microphone are positioned close to the user's ears.

[0080] The microphone support portion 214R is formed to protrude from the ear hook 220 toward the rear, and the reference microphone 204R is positioned on the rear side of the microphone support portion 214R. The microphone support portion 214R is connected to the microphone support portion 214F and further to the speaker support portion 213 via the ear hook 220.

[0081] <Effect> In the case of earphones, since the housing is small, it is more difficult to satisfy the causality constraint compared to headphones. However, by applying the present invention, the same effects as those of the first embodiment can be obtained even in open-ear type earphones.

[0082] <Modification> In the first embodiment, open-ear type headphones are assumed, and in the second embodiment, open-ear type earphones are assumed. However, the present invention can also be applied to open-ear type acoustic sound emitting devices, or more specifically, devices with less sound insulation by the housing (enclosure), such as open-back headphones and smart glasses. For example, open-back headphones have a driver unit that is not sealed, and the outside of the housing has a porous specification such as a mesh structure, and direct sound passes through the holes, and almost no reflection or absorption of direct sound occurs, and the user can directly hear the direct sound, so it corresponds to an open-ear type acoustic sound emitting device. Also, the present invention may be applied to open-ear type earphones of any shape. For example, a clip type that夹在耳朵下部 may be used (see Reference 2).

[0083] (Reference 2) "HUAWEI FreeClip", [online], [searched on November 5, 2024], Internet <URL:https: / / consumer.huawei.com / jp / audio / freeclip / > It may also have a sound emitting part arranged from the upper part of the ear toward the auricle direction, a structural part arranged from the upper part of the ear toward the Yifeng direction, and a connecting part of the two structural parts (see Reference 3).

[0084] (Reference 3) "Soundcore AeroFit", [online], [searched on November 5, 2024], Internet <URL:https: / / www.ankerjapan.com / products / a3872?variant=4335484<5970593> Also, the open-ear type earphones may be of a local sound emission type. The local sound emission type may be realized by directivity control or by using sound waves of opposite phase that are emitted on the side opposite to the ear direction.

[0085] <Other Modifications> The present invention is not limited to the embodiments and modifications described above. For example, the various processes described above may not only be performed sequentially according to the description, but may also be performed in parallel or individually as needed, depending on the processing capacity of the device performing the processes. Other modifications can be made as appropriate without departing from the spirit of the present invention.

Claims

1. An acoustic sound emitting device worn by a user, comprising: a sound-dampening speaker; a speaker support part for supporting the sound-dampening speaker; a reference microphone; a microphone support part for supporting the reference microphone; and a noise cancellation device that generates a sound-dampening signal using an acoustic signal picked up by the reference microphone, wherein when the acoustic sound emitting device is worn, the user can hear the direct sound of an acoustic signal coming from the outside; the sound-dampening speaker reproduces the sound-dampening signal; and the microphone support part is connected to the speaker support part and is configured to protrude in the direction relative to the speaker support part such that the reference microphone is positioned in a direction sensitive to human hearing characteristics.

2. The acoustic sound emission device according to claim 1, wherein the microphone support portion is configured such that the reference microphone is positioned in front of the user.

3. The acoustic sound emission device according to claim 2, wherein the microphone support portion is configured such that the reference microphone is positioned in front of the user and above the user's eyes.

4. An acoustic sound emission device according to claim 1, comprising one of the sound-dampening speaker, the speaker support, the reference microphone, and the microphone support for the left ear or one for the right ear, wherein the microphone support is configured to protrude in the direction relative to the speaker support for the left ear or the right ear, or comprising two of the sound-dampening speaker, the speaker support, the reference microphone, and the microphone support for both ears, wherein the microphone support is configured to protrude in the direction relative to the speaker support for both ears.

5. The acoustic sound emission device according to claim 1, wherein the microphone support portion is a hairband-shaped member that passes around the user's head.

Images