Temporary Hearing Threshold Shift Research Articles

The Influence of the Acoustic Properties of Motorcycle Helmets on Temporary Hearing Loss in Motorcyclists

Noise is an unavoidable component of motorcycling. The noise sources are varied, and include the helmet itself which also filters the noise passing through it. Here helmet noise transmission characteristics have been analyzed using insertion loss measurements and loudness matching in a behavioural study. Results demonstrate the action of the helmet as a spectral filter and confirm previously published data showing attenuation in the frequency range above 500 Hz. Highlighted here for the first time is an amplification of noise below 500 Hz. The loudness matching task data allowed the generation of equiloudness functions which show the effect of the helmet on riders' perceptions of loudness. The generated curves are here compared to the relevant international standard (ISO226) and show that loudness was strongly influenced by the helmet. The noise experienced by a motorcycle rider on a 30 minute journey can result in a temporary hearing threshold shift of over 15 dB. Due to the filtering characteristics of the helmet this threshold shift is highly frequency dependent. To quantify the frequency dependence of the resulting temporary hearing threshold shift pure tone audiometry was conducted before and after exposure to white noise, with and without a helmet in a laboratory setting and after on-road noise exposure. Of particular note is the finding of increased hearing sensitivity at high frequencies following certain type of motorcycle noise exposure. The difference is discussed in the framework of the filtering characteristics of the helmet.

Mechanical rock grinding in the Mississippi River: anthropogenic noise production and implications for the federally endangered pallid sturgeon, Scaphirhynchus albus (Forbes & Richardson, 1905)

Summary The use of mechanical rock grinding to remove rock pinnacles and outcroppings, considered to be navigation hazards in the Mississippi River, was evaluated as a less damaging alternative when compared to the more conventional use of drilling and blasting. The project area contains the federally endangered pallid sturgeon (Scaphirhynchus albus) and there was concern that intense sound pressure levels (SPLs) could impact the species. SPLs were measured during production rock grinding (January 2012, just north of Thebes, Illinois) and compared to those values with SPLs known to cause fish mortality, hearing damage, temporary hearing threshold shifts (TTS), and stress. The source SPLs’ maxima for each time block analyzed ranged from 160–172 dB (re 1 μPa @ 1 m) at frequencies ranging from 100–1250 Hz (1/3-octave band). The highest source SPL maximum recorded for the sound recording session was 172 dB (re 1 μPa @ 1 m) at 1250 Hz. These SPL levels at 1 m from the grinder were well below levels responsible for mortality or noise induced hearing damage. The impact zone for stress (increases in cortisol) was calculated to be within a 9 m radius of the grinder, while the impact zone for TTS was calculated to be within 31 m of the grinder. Considering the small impact zones and continuous noise production during grinding, there is a strong possibility that sturgeon would either avoid or move out of the impact zone.

3 Tesla magnetic resonance imaging noise in standard head and neck sequence does not cause temporary threshold shift in high frequency.

High acoustic noise level is one of the unavoidable side effects of 3 T magnetic resonance imaging (MRI). A case of hearing loss after 3 T MRI has been reported in this institution and hence this study. The objective of this study was to determine whether temporary threshold shift (TTS) in high frequency hearing occurs in patients undergoing 3 T MRI scans of the head and neck. A total of 35 patients undergoing head and neck 3 T MRI for various clinical indications were tested with pure tone audiometry in different frequencies including high frequencies, before and after the MRI scan. Any threshold change from the recorded baseline of 10 dB was considered significant. All patients were fitted with foamed 3 M earplugs before the procedure following the safety guidelines for 3 T MRI. The mean time for MRI procedure was 1,672 s (range 1,040-2,810). The noise dose received by each patient amounted to an average of 3,906.29% (1,415-9,170%). The noise dose was derived from a normograph used by Occupational Noise Surveys. This was calculated using the nomograph of L eq, L EX, noise dose and time. There was no statistically significant difference between the hearing threshold before and after the MRI procedures for all the frequencies (paired t test, P > 0.05). For patients using 3 M foamed earplugs, noise level generated by 3 T MRI during routine clinical sequence did not cause any TTS in high frequency hearing.

Frequency of greatest temporary hearing threshold shift in harbor porpoises (Phocoena phocoena) depends on the noise level.

Harbor porpoises may suffer hearing loss when they are exposed to high level sounds. After exposure for 60 min to a 6.5 kHz continuous tone at average received sound pressure levels (SPLav.re.) ranging from 118 to 154 dB re 1μPa, the temporary hearing threshold shifts (TTSs) of a harbor porpoise were quantified at the center frequency (6.5 kHz), at 0.5, 1.0, and 1.3 octaves above the center frequency (9.2, 13.0, and 16.0 kHz), and at a frequency assumed to be ecologically important for harbor porpoises (125 kHz, the center frequency of their echolocation signals) by means of a psychoacoustic technique. The hearing frequency at which the maximum TTS occurred depended on the SPLav.re. The higher the SPLav.re., the higher the TTS induced at frequencies higher than the exposure frequency; below 148 dB re 1 μPa, the maximum TTS was at 6.5 kHz, whereas above 148 dB re 1 μPa, the maximum TTS was at 9.2 kHz. The hearing threshold of the harbor porpoise for the center frequency of its echolocation signals (125 kHz) was not affected at the highest SPLav.re. to which the animal was exposed.

Hearing frequency thresholds of a harbor porpoise (Phocoena phocoena) temporarily affected by a continuous 1.5 kHz tone

Harbor porpoises may suffer hearing loss when exposed to intense sounds. After exposure to a 1.5 kHz continuous tone without harmonics at a mean received sound pressure level of 154 dB re 1 μPa for 60 min (cumulative sound exposure level: 190 dB re 1 μPa(2) s), the temporary hearing threshold shift (TTS) of a porpoise was quantified at 1.5, 2, 4, 6.5, 8, 16, 32, 63, and 125 kHz with a psychoacoustic technique. Significant TTS only occurred at 1.5 and 2 kHz. Mean TTS (1-4 min after sound exposure stopped) was ~14 dB at 1.5 kHz and ~11 dB at 2 kHz, and recovery occurred within 96 min. Control hearing tests before and after a 60 min low ambient noise exposure showed that normal variation in TTS was limited (standard deviation: ± 1.0 dB). Ecological effects of TTS depend not only on the magnitude of the TTS, its duration (depending on the exposure duration), and the recovery time after the exposure stopped, but also on the hearing frequency affected by the fatiguing noise. The hearing thresholds of harbor porpoises for the frequencies of their echolocation signals are not affected by intense low frequency sounds, therefore these sounds are unlikely to affect foraging efficiency.

Comparative temporary threshold shifts in a harbor porpoise and harbor seal, and severe shift in a seal

Anthropogenic noise may cause temporary hearing threshold shifts (TTSs) in marine mammals. Tests with identical methods show that harbor porpoises are more susceptible to TTS induced by octave-band white noise (OBN) centered around 4 kHz than harbor seals, although their unmasked (basic) hearing thresholds for that frequency are similar. A harbor seal was exposed for 1 h to an OBN with a very high sound pressure level (SPL), 22-30 dB above levels causing TTS onset. This elicited 44 dB TTS; hearing recovered within 4 days. Thus, for this signal and this single exposure, permanent threshold shift requires levels at least 22 dB above TTS onset levels. The severe TTS in the seal suggests that the critical level (above which TTS increases rapidly with increasing SPL) is between 150 and 160 dB re 1 μPa for a 60 min exposure to OBN centered at 4 kHz. In guidelines on TTS in marine mammals produced by policy makers in many countries, TTS is assumed to follow the equal energy hypothesis, so that when the sound exposure levels of fatiguing sounds are equal, the same TTS is predicted to be induced. However, like previous studies, the present study calls this model into question.

Involvement of retinoic acid-induced peroxiredoxin 6 expression in recovery of noise-induced temporary hearing threshold shifts

All-trans retinoic acid (ATRA) is reported to reduce hair cell loss and hearing deterioration caused by noise-induced hearing loss (NIHL). The present study investigates the involvement of peroxiredoxin 6 (Prdx 6) in ATRA-mediated protection of temporary threshold shift of hearing. Mice fed with ATRA before or after exposure to white noise showed a faster recovery than untreated controls within 1 week, with a concomitant increase of cochlear Prdx 6 expression. Treatment of mouse auditory cells with ATRA induced Prdx 6 expression. A putative retinoic acid (RA)-response element (RARE) was identified in a murine Prdx 6 promoter region. Prdx 6 promoter activities were elevated in wild-type reporter plasmid-transfected cells, whereas no significant change in activity was in those with RARE-disrupted mutant reporter. RA receptor α (RARα) functions as a transactivator of Prdx 6 gene expression. These findings suggest that ATRA-induced Prdx 6 expression may be associated with rapid recovery from temporary NIHL.

Temporary threshold shifts and recovery in a harbor porpoise (Phocoena phocoena) after octave-band noise at 4 kHz

Safety criteria for underwater sound produced during offshore pile driving are needed to protect marine mammals. A harbor porpoise was exposed to fatiguing noise at 18 sound pressure level (SPL) and duration combinations. Its temporary hearing threshold shift (TTS) and hearing recovery were quantified with a psychoacoustic technique. Octave-band white noise centered at 4 kHz was the fatiguing stimulus at three mean received SPLs (124, 136, and 148 dB re 1 μPa) and at six durations (7.5, 15, 30, 60, 120, and 240 min). Approximate received sound exposure levels (SELs) varied between 151 and 190 dB re 1 μPa(2) s. Hearing thresholds were determined for a narrow-band frequency-swept sine wave (3.9-4.1 kHz; 1 s) before exposure to the fatiguing noise, and at 1-4, 4-8, 8-12, 48, and 96 min after exposure. The lowest SEL (151 dB re 1 μPa(2) s) which caused a significant TTS(1-4) was due to exposure to an SPL of 124 dB re 1 μPa for 7.5 min. The maximum TTS(1-4), induced after a 240 min exposure to 148 dB re 1 μPa, was around 15 dB at a SEL of 190 dB re 1 μPa(2) s. Recovery time following TTS varied between 4 min and under 96 min, depending on the exposure level, duration, and the TTS induced.

Hearing threshold shifts and recovery in harbor seals (Phoca vitulina) after octave-band noise exposure at 4 kHz

Safety criteria for underwater sounds from offshore pile driving are needed to protect marine mammals. As a first step toward understanding effects of impulsive sounds, two harbor seals were exposed to octave-band white noise centered at 4 kHz at three mean received sound pressure levels (SPLs; 124, 136, and 148 dB re 1 μPa) at up to six durations (7.5, 15, 30, 60, 120, and 240 min); mean received sound exposure level (SEL) range was 166-190 dB re 1 μPa(2) s. Hearing thresholds were determined before and after exposure. Temporary hearing threshold shifts (TTS) and subsequent recovery were quantified as changes in hearing thresholds at 1-4, 4-8, 8-12, 48, and 96 min after noise exposure in seal 01, and at 12-16, 16-20, 20-24, 60, and 108 min after exposure in seal 02. Maximum TTS (1-4 min after 120 min exposure to 148 dB re 1 μPa; 187 dB SEL) was 10 dB. Recovery occurred within ~60 min. Statistically significant TTSs (>2.5 dB) began to occur at SELs of ~170 (136 SPL, 60 min) and 178 dB re 1 μPa(2) s (148 SPL, 15 min). However, SEL is not an optimal predictor of TTS for long duration, low SPL continuous noise, as duration and SPL play unequal roles in determining induced TTS.

Effects of Repeated “Benign” Noise Exposures in Young CBA Mice: Shedding Light on Age-related Hearing Loss

Temporary hearing threshold shift (TTS) resulting from a "benign" noise exposure can cause irreversible auditory nerve afferent terminal damage and retraction. While hearing thresholds and acute tissue injury recover within 1-2 weeks after a noise overexposure, it is not clear if multiple TTS noise exposures would result in cumulative damage even though sufficient TTS recovery time is provided. Here, we tested whether repeated TTS noise exposures affected permanent hearing thresholds and examined how that related to inner ear histopathology. Despite a peak 35-40 dB TTS 24 hours after each noise exposure, a double dose (2 weeks apart) of 100 dB noise (8-16 kHz) exposures to young (4-week-old) CBA mice resulted in no permanent threshold shifts (PTS) and abnormal distortion product otoacoustic emissions (DPOAE). However, although auditory brainstem response (ABR) thresholds recovered fully in once- and twice-exposed animals, the growth function of ABR wave 1( p-p ) amplitude (synchronized spiral ganglion cell activity) was significantly reduced to a similar extent, suggesting that damage resulting from a second dose of the exposure was not proportional to that observed after the initial exposure. Estimate of surviving inner hair cell afferent terminals using immunostaining of presynaptic ribbons revealed ribbon loss of ∼ 40 % at the ∼ 23 kHz region after the first round of noise exposure, but no additional loss of ribbons after the second exposure. In contrast, a third dose of the same noise exposure resulted in not only TTS, but also PTS even in regions where DPOAEs were not affected. The pattern of PTS seen was not entirely tonotopically related to the noise band used. Instead, it resembled more to that of age-related hearing loss, i.e., high frequency hearing impairment towards the base of the cochlea. Interestingly, after a 3rd dose of the noise exposure, additional loss of ribbons (another ≈ 25 %) was observed, suggesting a cumulative detrimental effect from individual "benign" noise exposures, which should result in a significant deficit in central temporal processing.

Tinnitus and hearing in 7-year-old children

BackgroundTinnitus occurs with or without prior noise exposure (noise-induced tinnitus (NIT) and spontaneous tinnitus (ST)), and is considered a symptom related to permanent hearing impairment (HI) or temporary hearing threshold...

Effects of Cigarette Smoking on Hearing Recovery From Noise-Induced Temporary Hearing Threshold Shifts in Mice

Cigarette smoking may potentiate noise-induced hearing loss. Many epidemiological studies have shown that cigarette smoking is a major risk factor for noise-induced hearing loss. BALB/c mice were exposed to passive smoking for 2 h/d for 2 weeks before exposure to 110-dB sound pressure level white noise for 3 hours once. Hearing was assessed via the auditory brainstem response with tone-burst stimulation and distortion product otoacoustic emissions before and at 1, 3, 5, 7, 14, 21, and 28 days after noise exposure. Oxidative stress and hypoxia were assessed by immunostaining with 8-oxoG and hypoxia-inducible factor 1α, respectively. Control mice unexposed to both smoking and noise and mice exposed to smoking only showed no shift in hearing threshold. In contrast, mice exposed to noise only or smoking plus noise showed abrupt increases in hearing threshold. In mice exposed to noise only, hearing threshold returned to prenoise levels after 2 weeks. However, in mice exposed to smoking plus noise, the loss of hearing was significantly higher, and hearing threshold did not return to the pre-exposure levels until 4 weeks later. Positive staining with 8-oxoG and hypoxia-inducible factor 1α were observed in the inner ear of the smoking-only and smoking-plus-noise group similar to noise-only mice, whereas no positive staining was observed in control group. These results indicate that cigarette smoking may potentiate the harmful effects of noise on hearing and disturb the recovery mechanism in the cochlea.

The effect on the temporary threshold shift in hearing acuity from combined exposure to authentic noise and hand-arm vibration

This study examined and compared the effect on temporary threshold shift in hearing (TTS) in healthy subjects of noise and hand-arm vibration (HAV) combined and separately using controlled and authentic exposure conditions. This study also investigated the effect on TTS in hearing in relation to gender after such exposures. Twenty-two healthy subjects (11 men/women, mean age 22 years, range 18-31years) were exposed both separately and in combination with HAV (6.7m/s(2)), using vibrating handles and to noise (99dB(A)) using headphones, for 20min. The HAV and noise were reproduced from recordings from angular grinder in operation. Hearing thresholds at 1, 4, and 8kHz were measured before and up to 30min after exposure. Combined exposure to noise and HAV created significantly greater TTS in hearing than HAV exposure at 4 and 8kHz alone. After exposure to HAV, there was no significant change in hearing threshold. At 1kHz, there was a significant difference between noise and HAV exposure in TTS in hearing. There was no significant difference between combined exposure and noise exposure for any test frequency. There was no significant difference in TTS in hearing in relation to gender for 1, 4, and 8kHz for HAV, noise, or a combined exposure. The results indicate that there is no difference in the TTS in hearing after combined exposure compared to noise exposure alone. HAV exposure did not change the hearing threshold. The TTS in hearing did not differ significantly in relation to gender after HAV, noise, or combined exposure.

Temporary hearing threshold shifts and recovery in a harbor porpoise (Phocoena phocoena) and harbor seals (Phoca vitulina) exposed to white noise in a 1/1‐octave band around 4 kHz.

To set safety criteria for levels of sounds produced during pile driving for offshore wind parks, temporary hearing threshold shifts (TTSs) were studied in a harbor porpoise and two harbor seals. A psychoacoustic behavioral technique was used to quantify TTS and hearing recovery in the animals exposed to underwater sounds (white noise in a 1/1‐octave band around 4 kHz). Hearing thresholds were determined once a day for a narrow‐band frequency swept sine wave (3.9–4.1 kHz) before and after exposure to the fatiguing noise, which was offered at two sound pressure levels (131 and 119 dB re 1 μPa for the porpoise and 151 and 139 dB re 1 μPa for the seals) each at four durations (15, 30, 60, and 120 min). Recovery was quantified by measuring hearing thresholds at 4, 8, 12, and 48 min after the noise exposure. The results show that TTS in harbor porpoises occurred at a sound exposure level threshold approximately 20 dB below the threshold for which TTS occurred in harbor seals.

Motorcycle helmets and the frequency dependence of temporary hearing threshold shift.

Temporary hearing threshold shifts (THTSs) as a result of exposure to noise vary as a function of the noise’s spectral content. However, to date THTS has been measured and predicted in a way that does not take account of frequency variation—most notably in standards such as British Standard 5330. We therefore carried out pure-tone audiometry on participants before and after exposure to white noise in order to quantify the frequency dependence of the THTS. Moreover, as this research group has previously shown that motorcycle helmets act as spectral filters, attenuating noise in the region above 500 Hz and amplifying noise in the regions below 500 Hz; this was done both with and without a motorcycle helmet. As our previous findings would suggest, the pattern of threshold shift is a function of the filter characteristics of the helmet, including an increased sensitivity at higher frequencies. There was also greater than expected reduction in sensitivity at frequencies where the helmet amplifies incident noise. The results indicate an acoustic effect of helmets which has not previously been reported.

Ingestion of Korean Red Ginseng after Noise Exposure Can Potentiate Rapid Recovery of Hearing in Mice

One mechanism of inner ear damage by noise-induced hearing loss (NIHL) is the production of reactive oxygen species (ROS). Because Korean red ginseng (KRG) has an anti-ROS effect in various tissues, KRG may have a role in preventing NIHL. A window period exists in which ROS formations continue after noise exposure, and further damage can be prevented by antioxidants. In this study, we aimed to investigate the effects of KRG after exposure to noise. KRG (200 mg/kg) was fed to mice for 3 days after noise exposure. The change in hearing level was analyzed by measuring the auditory brainstem response. To induce a temporary threshold shift (TTS) of hearing, mice were exposed to 110 dB white noise for 3 hours. Fast recovery of hearing was observed in mice fed KRG 1 hour and 1 day after noise exposure for 3 days. The expression of 8-oxoguanine was not observed in the inner ears of mice fed KRG 1 hour after noise exposure, but was evident in the stria vascularis of mice in the control group (noise exposure only). From this study, we conclude that KRG acted as an effective inhibitor of NIHL in TTS cases.

Temporary hearing loss influences post-stimulus time histogram and single neuron action potential estimates from human compound action potentials

An analytic compound action potential (CAP) obtained by convolving functional representations of the post-stimulus time histogram summed across auditory nerve neurons [P(t)] and a single neuron action potential [U(t)] was fit to human CAPs. The analytic CAP fit to pre- and postnoise-induced temporary hearing threshold shift (TTS) estimated in vivo P(t) and U(t) and the number of neurons contributing to the CAPs (N). The width of P(t) decreased with increasing signal level and was wider at the lowest signal level following noise exposure. P(t) latency decreased with increasing signal level and was shorter at all signal levels following noise exposure. The damping and oscillatory frequency of U(t) increased with signal level. For subjects with large amounts of TTS, U(t) had greater damping than before noise exposure particularly at low signal levels. Additionally, U(t) oscillation was lower in frequency at all click intensities following noise exposure. N increased with signal level and was smaller after noise exposure at the lowest signal level. Collectively these findings indicate that neurons contributing to the CAP during TTS are fewer in number, shorter in latency, and poorer in synchrony than before noise exposure. Moreover, estimates of single neuron action potentials may decay more rapidly and have a lower oscillatory frequency during TTS.

Hearing threshold shift measured by otoacoustic emissions after shooting noise exposure in soldiers using hearing protectors

The aim of the study was to assess the influence of short-term impulse noise to temporary threshold shift in soldiers using hearing protectors. The study included 80 subjects with correct tympanic membrane and thresholds measured by pure-tone audiometry less than 20 dB. There were two groups: 40 soldiers protected during shooting and 40 young males who didn't shoot. TEOAE were performed by ILO 292 Echoport Otodynamics device 3 to 5 minutes before shooting and 2 minutes and 1, 2, and 3 hours after shooting. Short-term exposure to impulse noise generated by five gunshots from the rifle kbk AKMS hasn't induced temporary threshold shift of hearing for chosen frequencies in soldiers using hearing protectors. Spectral analysis for chosen frequencies revealed that measurement reproducibility, stimuli level, and probe stability appeared to be comparable and repeatable. Our results show that the use of hearing protectors safeguarded against impulse noise. The use of earmuffs is strongly recommended because they seem to sufficiently attenuate shooting noise.

Ocena przydatności ochronników słuchu podczas narażenia na działanie hałasu impulsowego

It is generally agreed that impulse noise that occurs mainly in industrial processes, military forces and recreational target practice und hunting is especially hazardous to the ear. From the physical point of view the phenomenon is defined as an acoustic pressure disturbance of short duration less than 1 sec and high intensity with the peak sound pressure levels greater than 100 dB SPL. The study included 80 subjects (160 ears) aged 19-23 with correct tympanic membrane and thresholds measured by pure tone audiometry less than 20 dB. There were divided into two groups: I comprised 40 recruit soldiers put to the shooting training and group II consisted of 40 recruit soldiers using hearing protectors during shooting. Transient evoked otoacoustic emission (TEOAE) measurements were performed by ILO 292 Echoport Otodynamics device 3-5 min before shooting and then 2 min, 1, 2 and 3 hours respectively after shooting in both groups. It was found that the gunshot impulse noise from kbk AKMS rifle caused in group I temporary hearing threshold shift (TTS) for 1, 2, 3, 4 and 5 kHz frequencies of 1.07; 0.96; 1.41; 0.88 and 1.25 dB SPL respectively. TTS turned out to be maximum at 4 and 5 kHz and minimum at 1 and 2 kHz. In group II the soldiers used ear-muffs post-exposure changes were not significant. Short-term impulse noise generated by the rifle gunshots induced threshold shift of hearing. The usage of hearing protectors should be highly recommended because most of them seem to sufficiently attenuate impulse noise from firearms should be highly recommended because most of them seem to sufficiently attenuate impulse noise from firearms.

Temporary threshold shifts in the bottlenose dolphin (Tursiops truncatus), varying noise duration and intensity

There is much concern regarding increasing noise levels in the ocean and how it may affect marine mammals. However, there is a little information regarding how sound affects marine mammals and no published data examining the relationship between broadband noise intensity and exposure duration. This study explored the effects of octave-band noise on the hearing of a bottlenose dolphin by inducing temporary hearing threshold shifts (TTS). Sound pressure level (SPL) and exposure duration were varied to measure the effects of noise duration and intensity. Hearing thresholds were measured using auditory evoked potentials before and after sound exposure to track and map TTS and recovery. Shifts were frequency dependent and recovery time depended on shift and frequency, but full recovery was relatively rapid, usually within 20 min and always within 40 min. As exposure time was halved, TTS generally occurred with an increase in noise SPL. However, with shorter, louder noise, threshold shifts were not linear but rather shorter sounds required greater sound exposure levels to induce TTS, a contrast to some published literature. From the data a novel algorithm was written that predicts the physiological effects of anthropogenic noise if the intensity and duration of exposure are known.