In-ear noise measurement

Abstract

A hearing protection device to be worn in ear provides communications of ambient sound to an in-ear speaker. Blast noise is detected and measured using either the in-ear speaker as a microphone or using a separate in-ear microphone.

Description

IN-EAR NOISE MEASUREMENTCross-Reference to Related Applications

[0001] This application claims priority from U.S. Provisional Patent Application 63 / 696,593 filed September 19, 2024, the content of which is hereby incorporated by reference.Technical Field

[0002] This patent application relates to the field of hearing protection, and in particular to the measurement of impulsive and high stationary noise levels in the ear canal for monitoring of the exposure to excessive levels of sound in people such as workers and soldiers.

[0003] When working in environments that subject workers to noise stress, hearing protection devices and communication devices are commonly used. These devices combine the function of noise reduction and hearing protection, like passive earplugs, with electronic communications capabilities and the ability to digitally filter or process external sounds to be relayed to the worker. These devices may also be used to measure noise levels to which the worker is subjected.

[0004] Exposure to loud sounds can cause hearing loss, tinnitus, or both. Hearing loss is often caused by prolonged exposure to loud sounds from stationary sources (especially when hearing protection is not used or the auditory system does not have enough time to rest between exposures) but it can also happen from a single very loud exposure from impulse sources, such as that from firearm or a firecracker. The louder the sound, the shorter the amount of time it takes for hearing loss to occur. For stationary noises, the National Institute for Occupational Safety and Health (NIOSH) uses a 3-dB exchange rate which is also known as "trading ratio" or "time-intensity tradeoff, it basically means that for every 3-dB increase in noise exposure, measured in decibel (dB), the duration must be cut in half. Conversely, for every 3-dB decrease in noise exposure, duration of exposure can be doubled. For impulse noises, the exposure limits are set to the number of repetitions of peak instant values.

[0005] Personal noise exposure measurements aim to assess the amount of noise received by a given worker (civilian or military), to ensure this amount complies with the exposure limits set by a given legislation such as the OSHA standard. This assessment is preferably done using a personal body-worn noise dosimeter (PND), usually worn on the shoulder, which provides the convenience of continuous monitoring at the location of the individual. PNDs are particularlyuseful when individuals are required to move frequently during their work shift or when the acoustic environment of the workplace is hardly predictable, but they suffer from three major limitations:(i) in directional sound fields, large errors due to placement effects may occur,(ii) the measured sound pressure levels (SPL) may be affected by the wearer's own voice and,(iii) the accuracy of PNDs is compromised when hearing protection devices (HPD) are worn as the underlying sound attenuation (which should be subtracted from the ambient SPLs) can show large variations and uncertainties, as a function of time but also frequency content of the ambient noise.

[0006] Additionally, one could argue that standard PNDs only give information about the ambient cumulated SPLs on the worker’s body, while the risks of hearing damage is probably more related to the SPLs at the eardrum. Yet even in the absence of HPDs, a given ambient SPL may be associated with a wide range of in-ear SPLs, depending on sound incidence and subject morphology, resulting in large variabilities in noise exposure.

[0007] To remedy these issues, systems that continuously monitor an individual's noise exposure directly inside the ear canal -further referred to as in-ear noise dosimeters (IEND)- are continually expanding.

[0008] Unfortunately, the existing miniaturized microphone that can be embedded within lENDs suffer from a limited dynamic range: when the sound pressure level reaches peak levels above approximately 140 dB (that corresponds to the instant peak sound pressure level of a small firearm at arms length), typical miniaturized electret microphones will start to saturate, i.e., to clip or produce distorted recordings. While some microphone elements might support higher sound pressure level, they typically suffer from an elevated electrical noise-floor that prevent accurate exposure measurement for low to moderate ambient noise.

[0009] Finding a device and method for the in-ear measurement of impulsive and stationary noise levels of high amplitude is critical and particularly challenging given the small dimension constraints imposed by the use of in-ear devices.Summary

[0010] A hearing protection device to be worn in ear provides communications of ambient sound to an in-ear speaker. Blast noise is detected and measured using either the in-ear speaker asa microphone or using a separate in-ear microphone.

[0011] In some embodiments, there is provided a hearing protection and communications device to be worn in ear that has a proximal portion shaped to fit into an ear canal having a proximal end facing the ear canal, and a distal portion to fit outside the ear canal. A first in-ear microphone, having a dynamic range suitable for receiving sounds related to the voice of the wearer and nonblast, stationary ambient noise while clipping sounds of a blast in ambient noise can be provided in the proximal portion, along with an in-ear miniature loudspeaker. An outer-ear microphone can be located near or in the distal portion. The device can include a filter or audio processor operatively connected to the outer-ear microphone and the in-ear loudspeaker for selectively relaying ambient sounds to the wearer. A wireless transceiver can be operatively connected to the first in-ear microphone and the in-ear loudspeaker for full-duplex audio communications. For receiving in-ear blasts in ambient noise (e.g., intense noises), one of a blast receiver arrangement connected to the in-ear speaker for measuring a signal generated by the in-ear speaker during blasts in ambient noise, the blast receiver arrangement providing a blast signal output; and a second in- ear microphone having a blast signal output and located in the proximal portion having a lower sensitivity than the first in-ear microphone that is suitable for receiving sounds of a blast in ambient noise while being less sensitive to sounds related to the voice of the wearer. In some embodiments, a sound level meter is included in the device and is operatively connected to the first in-ear microphone for stationary noise and to the blast signal output for recording a time-series of each blast signal event and / or producing a sound exposure value that includes the effects of blast or impulse sound exposure.Brief Description of the Drawings

[0012] The invention will be better understood by way of the following detailed description of embodiments of the invention with reference to the appended drawings, in which:

[0013] Figure 1 is a view of a hearing protection device positioned on an ear pinna;

[0014] Figure 2A is side view of the hearing protection device of Figure 1 with the tail (“ear hook”) portion removed;

[0015] Figure 2B is a sectional view of the hearing protection device of Figure 2A;

[0016] Figure 2C is a schematic diagram of device of Figure 2A;

[0017] Figure 3 is a block diagram of one embodiment corresponding to Figure 2A;

[0018] Figure 4 is a block diagram of one embodiment corresponding to Figure 2C;

[0019] Figure 5 is a block diagram of another embodiment in which a dampened in-ear microphone is used.Detailed Description

[0020] Figure 1 shows a hearing protection device 10 according to one embodiment inserted into an ear canal. To help secure the device 10 to the ear canal, a tail portion or “ear hook” that wraps around the ear may be provided as illustrated. In this tail portion, a transmitter 30 and battery may be housed.

[0021] As illustrated in Figures 2A and 2B, a hearing protection device 10 typically features:• An external microphone 14 (Outer-Ear Microphone or OEM) to pick up ambient sounds.• An internal microphone 26 (In-Ear Microphone or IEM) to pick up the wearer's voice and residual noise underneath the earpiece.• A miniaturized loudspeaker (SPK) 20 to play back useful signals within the occluded ear canal of the wearer.

[0022] A digital signal processor 24 (DSP) shown in Figure 2C and corresponding audio interfaces ensure proper processing of the OEM ambient sounds. These sounds can be played back at a reduced / safe level in a "level-dependent" protector application or filtered to contain only useful signals such as speech and warning signals in a "smart" protector application through the loudspeaker SPK 20. For communication purposes, the audio signal picked up by the IEM 26, which typically contains the wearer's voice corrupted by some residual noise, can be filtered, enhanced, and transmitted through a wired or wireless interface (e.g., module 31 of Figure 3), such as a walkie-talkie, cell phone or personal radio, for example.

[0023] As shown in Figure 2A, the device 10 has a proximal portion 11 that is for insertion into the ear canal and a distal external portion 12. Sound insulation may be provided in the distal portion to attenuate sound before reaching the proximal portion. As best shown in Figure 2B, sound attenuation 16 can be provided in the proximal portion 11 while ports or tubes 22 and 28 can relay sound to the loudspeaker SPK 20 and IEM 26, respectively. While the sound attenuation is shown as being only in the proximal tip, attenuation may be provided elsewhere in the device 10 to provide the requisite level of attenuation, for example between 10 to 40 dB, depending on the frequency of interest and the proper fit of the device inside the ear canal. The OEM 14 is shownmounted to a small circuit board that may support a DSP 24. A transmitter 30,31 (such as a Bluetooth transmitter or the like), and a battery (not shown) may be contained in the device 10 via a cable connecting through port 32.

[0024] The signal from IEM 26 can also be used to record the exposure level of the worker inside the occluded ear canal, underneath the hearing protector's earpiece 10. This exposure can result from the ambient noise that passes passively through passive attenuation of the earpiece, the exposure resulting from electroacoustic transmission (through the OEM-DSP-SPK as mentioned above), and the exposure resulting from the wearer's own noise. This is referred to as "Wearer Induced Disturbances" and such signals contain the wearer's voice, as well as body noises (footsteps, hand-arm motion and body vibration induced noises, etc.). When the residual noise underneath the hearing protector is too high, the IEM sensor might saturate, making it impossible to measure accurately high levels of impulse noise, such as those typically resulting from impacts (in civilian industries) or firearms (in the military field).

[0025] The proposed device and method enable the measurement of in-ear sound pressure levels over a very wide dynamic range by combining the use of the existing, quite sensitive, IEM microphone with the use of the loudspeaker SPK 20, that acts as extra miniaturized sensor of decreased sensitivity.

[0026] In the embodiment of Figure 3, the OEM 14 provides a signal to a blast detection unit 34, to a filter or audio processor 24 and to a sound lever meter 36. This unit 34 may be provided by circuitry or might be provided by a DSP 24. When unit 34 detects a blast, such as a sound pressure level above a threshold level at which the IEM 26 would begin clipping or saturating, it triggers switch 25 to connect loudspeaker SPK 20 terminals to the sound level meter 36. The switch 25, unit 34 and meter 36 may cooperate to provide a blast receiver arrangement whether provided by circuit components or by a DSP. It will be appreciated that the dynamic range of OEM 14 may also be exceeded by a blast, and the sound level meter 36 may detect an impulse’s arrival using the signal from OEM 14 even if the blast itself would be clipped by the OEM 14. In such situation, the loudspeaker SPK 20 is no longer used as an actuator to play sounds inside the wearer's ear canal, but rather as sensor of less sensitivity particularly suitable for levels above 120 dB. This use of the speaker as an acoustic pressure sensor is made possible through the “acoustic reciprocity” property as featured for most transducer principle devices, such as electrodynamic, piezoelectric, etc. The blast detection circuit 34 may also signal to the sound level meter 36 to record the soundpressure level from loudspeaker SPK 20 instead of IEM 26.

[0027] The sound level associated with a blast or non-stationary noise can be a level higher than the stationary noise level of the working environment, and in particular, a level higher than the dynamic range of the IEM 26 used for picking up the wearer’s voice and stationary noise.

[0028] Detection of an impulse is important for monitoring noise exposure since a single blast can be a significant contributing factor to hearing loss and / or the time that a worker may continue to work in the environment without a break from noise exposure.

[0029] In an analog circuit implementation, the blast detection 34 can be a comparator whose output gates a switch 25 to provide the signal generated by the loudspeaker SPK 20 acting as a less-sensitive microphone to the sound level meter 36. If the sound level meter 36 is implemented in circuitry, it could comprise a number of comparators to measure the greatest value of the signal originating from loudspeaker SPK 20 during the blast. The sound level meter may also average and record the level of noise at the IEM 26. The sound level meter 36 may merge both signals originating from the IEM 26 and the loudspeaker SPK 20, as an impulse acoustic shock typically starts with a low-level magnitude, perfectly recorded by the IEM, and reaches high-level shortly after, perfectly recorded by the speaker used as an acoustic pressure sensor. Once, the signal from the IEM 26 is clipped because its dynamic range is exceeded, measurement of the blast spike waveform can rely on the less sensitive sensor 20. The detected and recorded data from meter 36 can be displayed or transmitted using the transmitter / di splay module 30.

[0030] When the blast detection is to be done digitally, the DSP 24 is the core component. As the DSP processes signals in a timeframe of given duration and because of the inherent delays of analog-to-digital conversion (ADC) then digital-to-analog (DAC) conversion, a substantial delay in the switching function may occur. As illustrated in Figure 4, loudspeaker SPK 20 can be connected to both an audio signal output port and to an audio signal input port of the DSP 24. The DSP may continuously record samples of the audio signal input port connected to loudspeaker SPK 20 in an audio First-in-First-Out (FIFO) buffer. When no blast occurs, this will be mostly the signal output by the DSP to the loudspeaker SPK 20. However, when a sample of the OEM 14 is first produced that exceeds a given threshold indicative of a blast, the DSP 24 may also stop retransmission of modulated audio from the OEM 14 to loudspeaker SPK 20 for the duration of the blast. The DSP 24 may also analyze the samples in the buffer from the IEM 26 and the in-ear loudspeaker SPK 20 to determine the impulse strength of the blast. Since the time to detect a blastby a DSP can be a significant portion of the duration of the blast impulse or even longer than the blast impulse, using buffered samples from the past can be important in assessing the blast. . It will be appreciated that the blast detection unit 34 and the sound level meter 36 can be implemented within the DSP 24.

[0031] It will thus be appreciated that the in-ear transducer, the loudspeaker SPK 20 can act as a pressure sensor, thanks to the acoustic reversibility principle. When a high-pressure soundwave reaches the occluded ear canal, it will be picked up by the IEM 26 and quickly saturate it, making the reading of the peak sound pressure level impossible. However, when this high-pressure soundwave reaches and moves the membrane of the loudspeaker SPK 20 (typically an electrodynamic transducer usually featuring a "balanced-armature loudspeaker” technology), the coil will produce a very small electrical current, and the corresponding low-voltage signal can be read by the audio interface. In this embodiment, the electrodynamic miniaturized loudspeaker SPK 20 may be simply the existing loudspeaker (SPK) 20 that is typically used to play back audio signals underneath the digital hearing protector, as described above. A digital signal processor 24 and proper audio interfaces 25 ensure that the loudspeaker's electrical connectors (connected to the audio output of the audio interface) are also connected to an audio input on the interface. When high-level noise is detected by the OEM 14 (e.g., when the sound pressure level is too high or by detecting saturation or "clipping" of the OEM microphone) and the corresponding « blast detector», the DSP 24 typically cuts the audio playback in a typical "level-dependent" hearing protector application. In the proposed embodiment, the DSP 24 would simultaneously cut all audio outputs to the SPK 20 and record the audio signal generated by the SPK as it senses the high- pressure soundwave. With its reduced sensitivity, the SPK 20 becomes a second sensor that complements the IEM 26 but will not saturate when high levels of noise are present underneath the hearing protector. When combined, into the so-called « Sound Level Meter » module 36 described in Figures 3 and 5, these two sensors 20 and 26 provide an accurate reading of the sound, whether stationary or impulsive, while conveniently fitting inside an in-ear device without additional sensor costs.

[0032] For illustration purposes, the maximum sound pressure level that can be instantly recorded by IEMS (these are "peak" values and should not be confused with equivalent or continuous levels) is approximately 120 dB for digital MEMS microphones and approximately 140 dB for analog electret microphones. As the passive attenuation of the earpiece typically rangesfrom 10 dB to 40 dB (depending on the frequency of the ambient noise and the quality of the earpiece's insertion into the ear canal), IEM sensor saturation can occur for ambient levels as low as 130 dB for digital microphones or 150 dB for more expensive analog electret microphones for low-frequency content. This level is not necessarily reached in civilian industries (as louder civilian environments generally have higher frequency noise), but is easily reached with any respectable firearm. This makes this invention of particular relevance for both civilian and military noise exposure assessment in hybrid noise environments (both impulsive and continuous).

[0033] Given the very small volume available for the IEM 26, and the needs for dynamic range and cost, an electret microphone can be a good choice. This does not exclude the option of using different types of microphone technology, such as magnetic coil based microphones, MEMS or piezoelectric based microphones.

[0034] Applicant has found however that the typical packaging and form factor of suitable electret microphones for use as an IEM can be easily adapted to lower their sensitivity such that blasts exceeding 140 dB can be accurately captured.

[0035] In the embodiment of Figure 5, the device 10 thus comprises two IEMS, namely IEM 26 and IEM 27. With reference to Figure 2B, the IEM 27 can be accommodated within the cavity of the earpiece 10. While it can be preferred to have IEM 27 connected via a tube to the proximal end of the earpiece just like IEM 26 is connected by its tube 28, it is also possible to have IEM 27 measure the sound pressure in the device 10 without a tube connecting it to pick up sound pressure in the ear canal. In this case, the sound level meter 36 will receive the signal from the IEM 27 during a blast and estimate the sound in the ear canal based on the measured level in the device 10. As illustrated in Figure 5, the blast detection unit 34 receives the signal from the OEM 14 and determines that there is a blast and at that point directs the signal from the lower sensitivity or dampened IEM 27 to the sound level meter 36.

[0036] It will be appreciated that the sound level meter 36 can be a device that records a full history of stationary and non-stationary noise to which the wearer has been exposed for the purposes of providing a report and / or a warning when exposure exceeds a standard or desired level, such as an OSHA standard. In some embodiments, the meter 36 may have a first component within the device 10 that acquires the soundwave time-signal data and transmits the data to a smartphone or other computing device having a second component of the meter 36 (e.g., an app in the computing device) that in turn can provide the necessary logging, analysis and / or display. Soundexposure warnings can be relayed to the wearer by generating tones or spoken word messages through the SPK 20.

[0037] The sound level meter 36 may record the waveform of the blast or impulse noise.Current methods (e.g., “ASEL” energy based, “Pfander”, using peak and time duration and “Auditory Hazard Assessment Algorithm for Humans” (AHAAH) based on a model of the ear) have shown that peak values and signal energy equivalent values may not represent the danger of exposure to a blast as well as other blast signal parameters such as rise time, time before first zero crossing (also known as the “A-duration”), signal envelope duration (also known as the “B- duration”), etc. Accurate recording of these time signals of short duration for subsequent analysis can lead to better understanding and management of blast noise management and response.

[0038] It is explicitly stated that all features disclosed in the description and / or the claims are intended to be disclosed separately and independently from each other for the purpose of original disclosure as well as for the purpose of restricting the claimed invention independent of the composition of the features in the embodiments and / or the claims. It is explicitly stated that all value ranges or indications of groups of entities disclose every possible intermediate value or intermediate entity for the purpose of original disclosure as well as for the purpose of restricting the claimed invention, in particular as limits of value ranges.

Claims

What is claimed is:

1. A hearing protection and communications device to be worn in ear and comprising: a proximal portion shaped to fit into an ear canal having a proximal end facing the ear canal; a distal portion to fit outside the ear canal; a first in-ear microphone, having a dynamic range suitable for receiving sounds related to the voice of the wearer and non-blast, stationary ambient noise while clipping sounds of a blast in ambient noise; an in-ear loudspeaker; an outer ear microphone located near or in the distal portion; a filter or audio processor operatively connected to the outer ear microphone and the in-ear speaker for selectively relaying ambient sounds to the wearer; a wireless transceiver operatively connected to the first in-ear microphone and the in-ear speaker for audio communications; for receiving in-ear blasts in ambient noise, one of a) a blast receiver arrangement connected to said in-ear speaker for measuring a signal generated by said in-ear speaker during blasts in ambient noise, said receiver providing a blast signal output; and b) a second in-ear microphone having a blast signal output and located in the proximal portion having a lower sensitivity than said first in-ear microphone that is suitable for receiving sounds of a blast in ambient noise while being less sensitive to sounds related to the voice of the wearer; and a sound level meter operatively connected to the first in-ear microphone for stationary noise and to the blast signal output for recording a time-series of each blast signal event and / or producing a sound exposure value that includes the effects of blast or impulse sound exposure.

2. The device as defined in claim 1, comprising said blast receiver arrangement, wherein said receiver comprises a switch connected to said in-ear loudspeaker, to said filter or audio processor and to said sound level meter, and a blast detection circuit connected to said outer ear microphone and providing a control signal to said switch.

3. The device as defined in claim 1, comprising said blast receiver arrangement, wherein said sound level meter and said filter or audio processor are provided by a digital signal processor (DSP), said receiver comprises an audio input port of said DSP connected to said in-ear speaker and a digital audio buffer of said DSP storing samples of said audio input port.

4. The device as defined in claim 1, comprising said second in-ear microphone.

5. The device as defined in claim 4, wherein said second in-ear microphone comprises a second tube for conducting sound between the second in-ear microphone and the ear canal.

6. The device as defined in any one of claims 1 to 5, wherein said first in-ear microphone comprises a tube for conducting sound between the first in-ear microphone and the ear canal, said tube passing through sound insulation of the proximal portion.

7. The device as defined in any one of claims 1 to 6, wherein said in-ear loudspeaker comprises a tube for conducting sound between the first in-ear microphone and the ear canal, said tube passing through sound insulation of the proximal portion.

8. The device as defined in any one of claims 1 to 7, wherein said sound level meter is configured to record the time-series of each said blast signal event.

9. The device as defined in any one of claims 1 to 8, wherein said sound level meter is configured to produce a sound exposure value that includes the effects of blast or impulse sound exposure.

10. The device as defined in claim 9, wherein said sound exposure value includes one or more of a rise time, a time before first zero crossing (“A-duration”), or a signal envelope duration (“B- duration”).

Images