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BR-112020022658-B1 - METHOD FOR ESTIMATING SOUND PRESSURE LEVEL, HEADPHONE SYSTEM, HEADPHONES AND HEADPHONE USE

BR112020022658B1BR 112020022658 B1BR112020022658 B1BR 112020022658B1BR-112020022658-B1

Abstract

Customized calibration methods and adapted devices identify acoustic corrections to be applied in intra-aural dosimetry. Acoustic corrections allow converting a measured acoustic pressure within a user's ear canal to an equivalent acoustic pressure at the eardrums and/or in a free field. The methods and devices also allow distinguishing noises originating from the user from ambient noise in the ear occluded by an earplug. This distinction is made using two microphones to simultaneously measure the acoustic pressure inside and outside the ear canal. The device can be used to determine a cumulative sound pressure level dosage to which a user is being exposed to surrounding sounds over a predetermined period of time.

Inventors

  • Fabien Bonnet
  • Jérémie Voix
  • HUGUES NÉLISSE
  • MARCOS NOGAROLLI

Assignees

  • IRSST - INSTITUT DE RECHERCHE EN SANTE ET EN SECURITE DU TRAVAIL DU QUEBEC
  • École De Technologie Supérieure

Dates

Publication Date
20260317
Application Date
20190509
Priority Date
20180509

Claims (20)

  1. 1. METHOD (50) FOR ESTIMATING AN INTRA-EAR SOUND PRESSURE LEVEL PERTINENT TO NOISE-INDUCED HEARING LOSS OF AN EAR CANAL (12) IN AN INDIVIDUAL, characterized by the method comprising: capturing a baseline external ear sound pressure level (Lp1) outside the ear canal (12); capturing a baseline intra-ear sound pressure level (Lp2) at an intermediate position (2) in the ear canal (12); determining a correction factor by identifying a pre-determined filter (62) and a standing wave frequency according to a difference between the captured baseline external ear sound pressure level (Lp1) and the captured baseline intra-ear sound pressure level (Lp2), while the ear canal (12) is not obstructed; after determining the correction factor, capturing (52) a first sound pressure level (Lp2, Lp2’) at the intermediate position (2) in the ear canal (12); estimate (57) the intra-aural sound pressure level according to the determined correction factor and the first captured sound pressure level, where estimating the intra-aural sound pressure level is converting the first captured sound pressure level into an equivalent tympanic sound pressure level.
  2. 2. METHOD (50), according to claim 1, characterized in that the first sound pressure level (Lp2, Lp2’) is captured behind a hearing protection device.
  3. 3. METHOD (50), according to claim 1, characterized by estimating the intra-aural sound pressure level without converting the first measured sound pressure level into an equivalent free-field sound pressure level (Lp3).
  4. 4. METHOD (50), according to claim 3, characterized in that the correction factor is calculated (55) by subtracting the captured baseline intra-aural sound pressure level (Lp2) from the captured baseline external ear sound pressure level (Lpx).
  5. 5. METHOD (50), according to claim 1, characterized by the method comprising: capturing a second sound pressure level from outside the ear canal (12) simultaneously with the capture of the first sound pressure level (Lp2, Lp2’), wherein the intra-aural sound pressure level relevant to noise-induced hearing loss is further estimated according to the second captured sound pressure level.
  6. 6. METHOD (50), according to claim 5, characterized by the estimation of the intra-aural sound pressure level relevant to noise-induced hearing loss, further comprising the calculation of an average ratio between two transfer functions associated with the first (Lp2, Lp2’) and second captured sound pressure levels.
  7. 7. METHOD (50), according to claim 6, characterized in that the average ratio between two transfer functions is determined for frequencies between a predetermined minimum frequency and a predetermined maximum frequency.
  8. 8. METHOD (50), according to claim 7, characterized in that the average ratio between two transfer functions associated with the first (Lp2, Lp2') and second captured sound pressure levels is defined as:
  9. 9. METHOD (50), according to claim 5, characterized in that the method further comprises detecting user-induced disturbance, wherein the effective intra-aural sound pressure level is further estimated according to the detected user-induced disturbance.
  10. 10. METHOD (50), according to claim 9, characterized in that the effective intra-aural noise level is further estimated according to a noise level of the detected user-induced disturbance, for frequencies between a predetermined minimum frequency and a predetermined maximum frequency.
  11. 11. METHOD (50), according to claim 10, characterized in that the noise level of the detected user-induced disturbance is determined by comparing the first captured sound pressure level (Lp2, Lp2’) with a threshold value of the noise level.
  12. 12. METHOD (40), according to claim 11, characterized in that the effective intra-aural sound pressure level is estimated according to the second captured sound pressure level when a user-induced disturbance is detected and when the noise level of the first captured sound pressure level is less than the noise level threshold.
  13. 13. METHOD (50), according to claim 9, characterized in that the user-induced disturbance is detected according to a coherence function between the first captured sound pressure level and the second captured sound pressure level.
  14. 14. METHOD (50), according to claim 13, characterized in that the user-induced perturbation is detected according to an average of the coherence function over a predetermined frequency range.
  15. 15. METHOD (50), according to claim 9, characterized in that the effective intra-aural sound pressure level is estimated ignoring the detected user-induced disturbance.
  16. 16. METHOD (50), according to claim 15, characterized in that the effective intra-aural sound pressure level is estimated according to the second captured sound pressure level and an estimated noise reduction.
  17. 17. METHOD (50), according to claim 16, characterized in that the estimated noise reduction is determined according to the first captured sound pressure level (Lp2, Lp2’) and the second captured sound pressure level performed when the average of the coherence function was less than the threshold value.
  18. 18. METHOD (50), according to claim 15, characterized in that the effective intra-aural sound pressure level is estimated according to the first sound pressure level (Lp2, Lp2’) captured when the average of the coherence function was less than the threshold value.
  19. 19. METHOD (50), according to claim 16, characterized in that the user-induced disturbance has a noise level that is less than a predetermined threshold noise level.
  20. 20. METHOD (50), according to claim 18, characterized in that the user-induced disturbance has a noise level that is higher than a predetermined threshold noise level.

Description

FIELD OF THE INVENTION [001] The present invention relates to the field of noise exposure measurement. More particularly, the present invention relates to the field of effective intra-aural sound exposure. BACKGROUND OF THE INVENTION [002] Every day, hundreds of millions of workers worldwide are exposed to noise levels that are likely to affect their hearing. Noise in the workplace remains a major concern, not only in developing countries but also in many developed countries. In 2000, 7% of European workers reported that their work activities had affected their health and led to hearing disorders. And yet, noise-induced hearing loss (NIHL) is, in practice, preventable, provided that excessive noise exposure of affected workers is detected before it is too late. Unfortunately, often the safety measures that could prevent NIHL are not applied because workers at risk are not actually aware that they are putting their hearing at risk. These measures may include noise control measures, the use of appropriate hearing protection devices (HPDs), or administrative controls such as the introduction of shorter working hours. To ensure the timely implementation of such measures, it is essential that the noise exposure levels of each individual are precisely established in the workplace. [003] Personal noise exposure measurements aim to assess a person's noise exposure, usually a worker, to ensure compliance with occupational exposure thresholds under specific legislation. This assessment is typically done by determining two variables: the ambient (unprotected) noise levels received by the individual and the attenuation provided by the HPD (if HPDs are being used). Ambient noise levels can be estimated using standard sound level meters or, for greater accuracy, using personal dosimeters worn on the body. Personal noise dosimeters are particularly useful in situations where the acoustic environment varies significantly over time, as these devices can track sound exposure near the individual's ears (they are usually worn on the shoulder). However, current issues relate to microphone placement effects and the influence of the user's voice on noise measurements, and cannot account for the attenuation provided by potential HPDs. Furthermore, despite the progress made in estimating the field performance of HPDs, current fit testing methods still suffer from a number of uncertainties that make it difficult to establish the effective attenuation of a particular HPD on a given individual. Finally, personal noise dosimeters only provide information on ambient noise levels; therefore, they do not take into account the effects of user placement and inter-individual differences in the ear geometries of users. Different people subjected to the same ambient noise level may effectively receive significantly different sound pressure levels (SPL) at the eardrum, and the intra-aural SPL levels received by a given person may also vary as a function of their head and body orientation. And although the damage risk criteria of existing noise standards refer to free-field measurements, it is generally believed that the risk of hearing loss is more directly related to the levels received at the tympanic membrane or eardrum. [004] In light of the issues mentioned above, promising systems have begun to emerge that provide continuous monitoring of an individual's noise exposure directly within the ear. These systems are not only capable of accounting for HPD attenuation, but they are also sensitive to the effects of user placement and the unique shape of each individual's ears. However, current in-ear noise dosimeters (IENDs) do not allow for direct data collection from the eardrum, as their in-ear microphone is typically held at a certain distance from the membrane for comfort and safety reasons. Therefore, a correction is necessary to convert the measured SPLs to the eardrum. While an average correction can be used, such as that measured on a mannequin, individual correction factors should provide better results, considering the very distinct geometry of each ear canal. Furthermore, personal noise exposure measurements aim to assess the amount of noise exposure a person, usually a worker, receives to ensure that this amount complies with the exposure thresholds of a given legislation. One way to monitor exposure levels is with a personal body dosimeter, which offers the convenience of continuous monitoring at the individual's location. Personal noise dosimeters are particularly useful when individuals need to move frequently during their work shift or when the workplace's acoustic environment is difficult to predict, as such variables cannot be accounted for with standard sound level meter measurements. They are generally placed on the user's shoulder to measure noise levels near the ears. While adequate, this location does not always neutralize the effect of microphone placement, particularly for directional sound fields. Furthermore, the measu