Listening level of music through headphones in train car noise environments

Threshold Equalizing Noise Test Reveals Suprathreshold Loss of Hearing Function, Even in the "Normal" Audiogram Range

Objectives:

The threshold equalizing noise (TEN(HL)) is a clinically administered test to detect cochlear “dead regions” (i.e., regions of loss of inner hair cell [IHC] connectivity), using a “pass/fail” criterion based on the degree of elevation of a masked threshold in a tone-detection task. With sensorineural hearing loss, some elevation of the masked threshold is commonly observed but usually insufficient to create a “fail” diagnosis. The experiment reported here investigated whether the gray area between pass and fail contained information that correlated with factors such as age or cumulative high-level noise exposure (>100 dBA sound pressure levels), possibly indicative of damage to cochlear structures other than the more commonly implicated outer hair cells.

Design:

One hundred and twelve participants (71 female) who underwent audiometric screening for a sensorineural hearing loss, classified as either normal or mild, were recruited. Their age range was 32 to 74 years. They were administered the TEN test at four frequencies, 0.75, 1, 3, and 4 kHz, and at two sensation levels, 12 and 24 dB above their pure-tone absolute threshold at each frequency. The test frequencies were chosen to lie either distinctly away from, or within, the 2 to 6 kHz region where noise-induced hearing loss is first clinically observed as a notch in the audiogram. Cumulative noise exposure was assessed by the Noise Exposure Structured Interview (NESI). Elements of the NESI also permitted participant stratification by music experience.

Results:

Across all frequencies and testing levels, a strong positive correlation was observed between elevation of TEN threshold and absolute threshold. These correlations were little-changed even after noise exposure and music experience were factored out. The correlations were observed even within the range of “normal” hearing (absolute thresholds ≤15 dB HL).

Conclusions:

Using a clinical test, sensorineural hearing deficits were observable even within the range of clinically “normal” hearing. Results from the TEN test residing between “pass” and “fail” are dominated by processes not related to IHCs. The TEN test for IHC-related function should therefore only be considered for its originally designed function, to generate a binary decision, either pass or fail.

Consumer-Grade Headphones for Children: Limited Effectiveness of "Level Limiters" When Used With Portable or Home Media Players

Consumer-grade headphones for children are frequently packaged or marketed with labels claiming incorporation of an output-level-limiting function. Six pairs of headphones, sold separately from devices with audio interfaces, were selected either from online recommendations or from “best rated” with a large online retailer, the opinions being expressed in 2018 to early 2019. The acoustic outputs in response to an internationally standardized test signal were measured through the ears of a head-and-torso simulator and referenced to equivalent A-weighted diffuse-field sound pressure levels. The headphones were tested with a variety of music capable sources found in a domestic environment, such as a mobile phone, tablets, laptop computer, and a home “hi-fi” CD player. To maintain likely homogeneity of the audio interface, the computer-based platforms were manufactured by either Apple™ or certified Android devices. One of the two Bluetooth-linked headphones exhibited level limiting with low distortion (i.e., a compression ratio well in excess of unity). None of the devices wired directly to an audio output performed distortionless level limiting: “limiting” was implemented by a reduction of sensitivity or mechanical limitations, so could be called “soft limiting.” When driven by a laptop or CD player, some were still capable of producing output levels well in excess of “safe-listening” levels of 85 dB(A). Packaging labels were frequently ambiguous and imprecise.

No Reliable Association Between Recreational Noise Exposure and Threshold Sensitivity, Distortion Product Otoacoustic Emission Amplitude, or Word-in-Noise Performance in a College Student Population

OBJECTIVES

The purpose of this study was to evaluate the relationship between recreational sound exposure and potentially undiagnosed or subclinical hearing loss by assessing sound exposure history, threshold sensitivity, distortion product otoacoustic emission (DPOAE) amplitudes, and performance on the words-in-noise (WIN) test.

DESIGN

Survey data were collected from 74 adult participants (14 male and 60 female), 18 to 27 years of age, recruited via advertisements posted throughout the University of Florida campus. Of these participants, 70 completed both the survey and the additional functional test battery, and their preferred listening level was measured in a laboratory setting.

RESULTS

There were statistically significant relationships between hearing thresholds and DPOAE amplitude. In contrast, performance on the WIN was not reliably related to threshold sensitivity within this cohort with largely normal hearing. The two most common exposures included bars or dance clubs, followed by music player use. There were no statistically significant relationships between individual or composite measures of recreational sound exposure, including preferred listening level, years of music player use, number of reported sound exposures, previous impulse noise exposure, or previous noise-induced change in hearing, and functional measures including threshold, DPOAE amplitude, and WIN measures. Some subjects were highly consistent in listening level preferences, while others were more variable from song to song.

CONCLUSIONS

No reliable relationships between common recreational sound exposure or previous noise-induced changes in hearing were found during analysis of threshold sensitivity, DPOAE amplitude, or WIN performance in this cohort. However, the study sample was predominantly female and Caucasian, which limits generalizability of the results.

The effect of brief subway station noise exposure on commuter hearing

Objective

To demonstrate that brief exposure to subway noise causes temporary threshold shift and is preventable with noise protection.

Methods

The study was conducted as a randomized crossover trial. Twenty subjects were randomly assigned to two groups, one with hearing protection and one without. Subjects were exposed to subway platform noise for 15 minutes. Pre‐ and post‐exposure pure tone audiometry (PTA) and otoacoustic emissions were compared. After a washout period, subjects switched hearing protection groups and repeated the process.

Results

A statistically significant reduction in PTA thresholds after subway noise exposure was identified, for subjects with and without hearing protection (P < .001). For exposure without hearing protection, the mean threshold was 5.19 dB pre‐exposure and 3.91 dB post‐exposure (decrease of 1.28 dB; 95% confidence interval, 0.82–1.74). For exposure with hearing protection, the mean threshold was 4.81 dB pre‐exposure and 3.47 dB post‐exposure (decrease of 1.34 dB; 95% confidence interval, 0.89–1.79).

Conclusion

Brief exposure to subway noise did not cause hearing loss with or without noise protection. Though clinically insignificant, the unexpected finding of reduction in PTA suggests that there are complex heterogeneous short‐ and long‐term cochlear responses to noise exposure that should be further explored.

Level of Evidence

1b

Amplitude-modulation detection by recreational-noise-exposed humans with near-normal hearing thresholds and its medium-term progression

Noise exposure can affect the functioning of cochlear inner and outer hair cells (IHC/OHC), leading to multiple perceptual changes. This work explored possible changes in detection of amplitude modulation (AM) at three Sensation Levels (SL) for carrier frequencies of 3, 4 and 6 kHz. There were two groups of participants, aged 19 to 24 (Young) and 26 to 35 (Older) years. All had near-normal audiometric thresholds. Participants self-assessed exposure to high-level noise in recreational settings. Each group was sub-grouped into low-noise (LN) or high-noise (HN) exposure. AM detection thresholds were worse for the HN than for the LN sub-group at the lowest SL, for the males only of the Young group and for both genders for the Older group, despite no significant difference in absolute threshold at 3 and 4 kHz between sub-groups. AM detection at the lowest SL, at both 3 and 4 kHz, generally improved with increasing age and increasing absolute threshold, consistent with a recruitment-like process. However, poorer AM detection was correlated with increasing exposure at 3 kHz in the Older group. It is suggested that high-level noise exposure produces both IHC- and OHC-related damage, the balance between the two varying across frequency. However, the use of AM detection offers poor sensitivity as a measure of the effects.