Reference Equivalent Threshold Sound Pressure Research Articles

Reference equivalent threshold sound pressure levels for the Wireless Automated Hearing Test System.

This paper presents reference equivalent threshold sound pressure levels (RETSPLs) for the Wireless Automated Hearing Test System (WAHTS), a recently commercialized device developed for use as a boothless audiometer. Two initial studies were conducted following the ISO 389-9 standard [ISO 389-9 (2009). "Acoustics-Reference zero for the calibration of audiometric equipment. Part 9: Preferred test conditions for the determinations of reference hearing threshold levels" (International Organization for Standardization, Geneva)]. Although the standard recruitment criteria are intended to yield otologically normal test subjects, the recruited populations appeared to have slightly elevated thresholds [5-10 dB hearing level (HL)]. Comparison of WAHTS thresholds to other clinical audiometric equipment revealed bias errors that were consistent with the elevated thresholds of the RETSPL populations. As the objective of RETSPLs is to ensure consistent thresholds regardless of the equipment, this paper presents the RETSPLs initially obtained following ISO 389-9:2009 and suggested correction to account for the elevated HLs of the originally recruited populations. Two additional independent studies demonstrate the validity of these corrected thresholds.

Utilizing True Wireless Stereo Earbuds in Automated Pure-Tone Audiometry.

True wireless stereo (TWS) earbuds have become popular and widespread in recent years, and numerous automated pure-tone audiometer applications have been developed for portable devices. However, most of these applications require specifically designed earphones to which the public may not have access. Therefore, the present study investigates the accuracy of automated pure-tone audiometry based on TWS earbuds (Honor FlyPods). The procedure for developing an automated pure-tone audiometer is reported. Calibration of the TWS earbuds was accomplished by electroacoustic measurements and establishing corrected reference equivalent threshold sound pressure levels. The developed audiometer was then compared with a clinical audiometer using 20 hearing-impaired participants. The average signed and absolute deviations between hearing thresholds measured using the two audiometers were 3.1 dB and 6.7 dB, respectively. The overall accuracy rate in determining the presence/absence of hearing loss was 81%. The results show that the proposed procedure for an automated air-conduction audiometer based on TWS earbuds is feasible, and the system gives accurate hearing level estimation using the reported calibration framework.

Reference equivalent threshold sound pressure levels for Apple EarPods.

Reference equivalent threshold sound pressure levels (RETSPLs) are used when calibrating audiometric equipment to a hearing threshold level of zero at various frequencies. To the best of the authors' knowledge, the RETSPLs for Apple EarPods (MB770G) have not been reported, and so this study aimed to measure them. The hearing thresholds of 36 normal-hearing subjects (72 ears) were measured at 250, 500, 1000, 2000, 4000, and 8000 Hz, with the measurements being performed twice in 33 subjects (66 ears) for evaluating the test-retest reliability. This study provides Apple EarPod RETSPLs and shows significant Pearson's correlations (p < 0.001) with no significant Wilcoxon signed-rank test differences (p > 0.01), which confirm the test reliability.

Calibration of brief stimuli for the recording of evoked responses from the human auditory pathway.

The relationship between the calibration RETSPL-values (reference equivalent threshold sound pressure level) in dB p-p.e.SPL and the corresponding sound pressure levels in dB SPL for brief stimuli is formulated mathematically. The formula is applied on ten brief stimuli consisting of a click, four tone-bursts, a chirp, and four octave-band chirps presented at a stimulus rate of 20 stimuli per second, and using the average acoustical parameter-values from a sample of 20 ER-3A insert earphones in the occluded-ear simulator. The reference calibration values in dB SPL for the ten stimuli are then established. These theoretical values are verified by direct measurements using two different sound-level-meters. It is concluded that the calibration values in dB SPL can be applied in the practical calibration of common brief stimuli. Calibration with these reference values involves only a sound-level meter, and the need for including an oscilloscope in the calibration setup is therefore eliminated.

Distribution characteristics of normal pure-tone thresholds

Objective: This study examined the statistical properties of normal air-conduction thresholds obtained with automated and manual audiometry to test the hypothesis that thresholds are normally distributed and to examine the distributions for evidence of bias in manual testing. Design: Four databases were mined for normal thresholds. One contained audiograms obtained with an automated method. The other three were obtained with manual audiometry. Frequency distributions were examined for four test frequencies (250, 500, 1000, and 2000 Hz). Study sample: The analysis is based on 317 569 threshold determinations of 80 547 subjects from four clinical databases. Results: Frequency distributions of thresholds obtained with automated audiometry are normal in form. Corrected for age, the mean thresholds are within 1.5 dB of reference equivalent threshold sound pressure levels. Frequency distributions of thresholds obtained by manual audiometry are shifted toward higher thresholds. Two of the three datasets obtained by manual audiometry are positively skewed. Conclusions: The positive shift and skew of the manual audiometry data may result from tester bias. The striking scarcity of thresholds below 0 dB HL suggests that audiologists place less importance on identifying low thresholds than they do for higher-level thresholds. We refer to this as the Good enough bias and suggest that it may be responsible for differences in distributions of thresholds obtained by automated and manual audiometry.

Earphones in extended high-frequency audiometry and ISO 389-5

Objective: To determine common reference equivalent threshold sound pressure levels (RETSPL) for the earphones used in the extended high-frequency (EHF) range, as different earphones are commercially available, but there are not RETSPLs for each model. Design: Hearing threshold sound pressure levels were measured up to 20 kHz for the Sennheiser HDA 200 audiometric earphone, and were compared to the ISO 389-5 (2006) norm and other investigations using that earphone and different ones. Study sample: A total of 223 otologically-normal subjects (aged 5–25 years old) participated in the hearing determination. Results: The results are in good agreement with previous studies of hearing thresholds using the same and other earphones. Conclusions: The results of the present investigation are relevant for the international standard for the calibration of audiometric equipment in the 8 to 16 kHz frequency range, ISO 389-5. The data may be used for a future update of the RETSPL for circumaural and insert audiometric earphones.

AMTAS®: Automated method for testing auditory sensitivity: III. Sensorineural hearing loss and air-bone gaps

Objective: The objectives were to measure the occlusion effect produced by three earphones—circumaural, supra-aural, and insert—and to compare air- and bone-conduction thresholds obtained with manual and automated methods for subjects with sensorineural hearing loss. Design: Acoustic and psychoacoustic occlusion effects were measured with each earphone. Manual and automated, air- and bone-conduction thresholds were compared. Study sample: Occlusion effects were measured for six adult subjects with normal external and middle ears. Pure-tone thresholds were measured for nineteen ears of thirteen subjects with sensorineural hearing loss. Results: The supra-aural earphone produced the largest occlusion effects, followed by the insert and circumaural earphones. Some systematic differences in air-conduction thresholds were found for the two procedures that may be attributable to earphone differences. A large air-bone gap at 4 kHz, reported in a previous study, was replicated. Conclusions: From 0.5 to 8.0 kHz, occlusion effects produced by the circumaural earphone are sufficiently small that covering the ear does not appreciably alter bone-conduction thresholds. Air-conduction threshold differences warrant further study to determine if reference equivalent threshold sound pressure levels for the two earphones produce equivalent thresholds. The large air-bone gap at 4 kHz suggests the possibility of an incorrect reference equivalent threshold force level at that frequency.SumarioObjetivo: Los objetivos fueron medir el efecto de oclusión producido por tres auriculares – circumaural, supra-aural y de inserción – y comparar umbrales de conducción aérea y ósea obtenidos con métodos manuales y automatizados para sujetos con hipoacusia sensorineural. Diseño: Se midieron los efectos de oclusión acústicos y psicoacústicos con cada auricular. Se compararon los umbrales de conducción aérea y ósea manuales y automatizados. Muestra del Estudio: Se midieron los efectos de oclusión para seis sujetos adultos con oídos externos y medios normales. Resultados: Los auriculares supra-aurales produjeron los mayores efectos de oclusión, seguidos de los auriculares de inserción y los circumaurales. Se encontraron algunas diferencias sistemáticas en los umbrales de conducción aérea para los dos procedimientos que pueden atribuirse a las diferencias en los auriculares. Una gran brecha aéreo-ósea en 4 kHz que se reportó en un estudio previo, fue replicada. Conclusiones: De 0.5 a 8 kHz, los efectos de oclusión producidos por los auriculares circumaurales son lo suficientemente pequeños por lo que cubrir el cubrir el oído no altera apreciablemente los umbrales de conducción ósea. Las diferencias en los umbrales de conducción aérea exigen estudios adicionales para determinar si los niveles umbrales equivalentes de referencia de presión sonora para los dos auriculares producen umbrales equivalentes. La mayor brecha aéreo-ósea en 4 kHz sugiere la posibilidad de un nivel de referencia equivalente de fuerza umbral en esa frecuencia.

Equivalent threshold sound pressure levels (ETSPL) for Interacoustics DD 45 supra-aural audiometric earphones

This paper describes the determination and results of pure-tone equivalent threshold sound pressure levels for the Interacoustics DD 45 audiometric earphone equipped with standard Model 51 cushions. The size and shape of the DD 45 transducer resembles the classic Telephonics TDH 39 earphone. Pure-tone hearing threshold measurements were performed for both ears of 29 test subjects. All audiometric frequencies from 125 to 8000 Hz were used. The data are intended for inclusion in future standardized reference equivalent threshold sound pressure levels. The results show that the DD 45 may be a good substitute for the THD 39 without the traditional 5-dB problem at 6000 Hz.SumarioEste trabajo describe la determinación y los resultados de los niveles de presión sonora para umbrales equivalente de tonos puros, con auriculares audiométricos Interacoustics DD 45 equipados con amortiguadores estándar Modelo 51. El tamaño y la forma de los transductores DD 45 se parecen al auricular clásico Telephonics TDH 39. Se realizaron mediciones de umbrales auditivos con tonos puros en ambos oídos de 29 sujetos de estudio. Se usaron todas las frecuencias audiométricas desde 125 a 8000 Hz. Los datos serán incluidos en referencias futuras de estandarización de presión sonora para umbrales equivalentes. Los resultados muestran que los DD 45 pueden ser un buen sustituto para los TDH 39 sin el problema tradicional de 5-dB en 6000 Hz.

Air and bone conduction evoked potential audiometry in the northern elephant seal

Elephant seals (Mirounga angustirostris) are the largest and most aquatic of the pinnipeds, spending up to eight months of the year at sea diving to depths as great as 1600 m. The pinna is absent in the elephant seal and the middle ear cavity and auditory canal are lined with a cavernous tissue, both of which are likely adaptations to deep diving. Elephant seals demonstrate a greater sensitivity to low frequency sounds than do other pinnipeds and an overall greater sensitivity to underwater sound than to airborne sound. The relative importance of sound conduction pathways in the elephant seal is undetermined, although it has been speculated that bone conduction pathways are important to underwater hearing in this species. To compare the sensitivity of the elephant seal to both air and bone conducted stimuli, auditory evoked responses were recorded in seals exposed to signals presented through headphones and via a bone vibrator. In comparison to airborne stimuli, bone conduction methods provide an opportunity to more effectively study sensitivity to low frequency sounds, but are challenged by a lack of reference equivalent threshold sound pressure levels. Future efforts should compare bone conduction and direct field audiometry results obtained within the same individual.

Reducing hearing protector test time with a minimum audible pressure to field transfer function

Effective hearing-loss prevention programs should train workers to properly fit hearing protection devices. In order to minimize the training time for protector fitting, unoccluded minimum audible field threshold (MAF) for narrow-band noise could be estimated from the worker’s annual minimum audible pressure (MAP) audiogram. Murphy et al. previously reported a transfer function for 5- and 1-dB audiometry for 75 and 10 subjects, respectively [W. J. Murphy, J. R. Franks, S. L. Hall, and E. F. Krieg, J. Acoust. Soc. Am. 101, 3126 (1997)]. Significant differences at several frequencies between the 1- and 5-dB groups prompted further study of the transfer function. This paper reports MAF and MAP results for 44 subjects tested with both 1- and 5-dB audiometry and 1-dB sound field. Pure-tone thresholds were significantly different, for 1- and 5-dB step sizes. The binaural reference equivalent threshold sound pressure level (RETSPL) sound-field thresholds were compared with the RETSPL thresholds for monaural listening in a sound-field listed in ANSI S3.6-1996, Table 9. The binaural thresholds were found to be significantly higher (p&amp;lt;0.05) than the standard values at all frequencies except 8000 Hz.

High-frequency (8–20 kHz) reference thresholds for audiometry

ANSI (S3.6-1996) and ISO (CD 389-5, 1996) have reported interim high-frequency (8–16 kHz) reference equivalent threshold sound pressure levels (RETSPLs). Since the interim RETSPLs were derived using very limited data, there is a need to increase the data base for specifying high-frequency RETSPLs. Thus, this study determined high-frequency (8–20 kHz) thresholds for 50 young adults having normal low-frequency (0.25–8 kHz) hearing across four test sessions, separated by at least one day, using Sennheiser HDA 200 and Koss HV/Pro earphones. The mean thresholds increased as frequency increased, especially at 16 kHz and above, and were similar to the ANSI and ISO interim RETSPLs. However, the standard deviations were very high and the range scores were very wide for each earphone at each frequency. This would indicate that specifying high-frequency RETSPLs may not be feasible due to very high intersubject threshold variability. On the other hand, the intrasubject threshold differences across each possible test session comparison were found to be very repeatable and within a clinically acceptable range. This would indicate the usefulness of high-frequency audiometry for monitoring patients having or suspected of having otopathology. [Work supported by the Pennsylvania Lions Hearing Research Foundation.]

Normal hearing levels for an ER‐3A insert earphone

Equivalent threshold sound pressure levels were obtained on each ear of 48 normal hearing adult subjects from 125–8000 Hz using TDH‐49P earphones, referenced to a NBS‐9A coupler, and ER‐3A insert earphones, referenced to a HA‐2 coupler. At each frequency (N = 9), the thresholds were significantly higher for the TDH‐49P than for the ER‐3A; however, the test versus retest and right versus left ear thresholds were not significantly different. The unadjusted ER‐3A thresholds were in agreement with the reference equivalent threshold sound pressure levels (RETSPLs) reported by ISO [ISO 389, DAD 3, 1990]. After correcting for the subject's deviation from normal TDH‐49P hearing levels and coupler (HA‐2 to HA‐1), the ER‐3A thresholds were also in agreement with interim REISPLs reported by ANSI [ANSI S3.6‐1989, Appendix G]. A complete data base concerning normative ER‐3A thresholds will be presented and discussed in reference to the results of the present study, ISO and ANSI RETSPLs, and for future standardization.

Electroacoustic calibration for sound field warble tone thresholds.

Walker, Dillon, and Byrne (1984) suggested reference equivalent threshold sound pressure levels (RETSPLs) for warble tones with specific modulation parameter values audited from a test position at the critical distance in a semireverberant sound field. This study evaluated these RETSPLs in two typical audiometric rooms and with typically encountered FM tones. Thresholds were measured under earphones and in two sound fields for 6-11 normal hearers at six test frequencies. Results indicated that there was a small but statistically significant difference between earphone and sound field thresholds in 4 of 24 comparisons. However, in both sound fields, 99% of the sound field thresholds were within 10 dB of the earphone thresholds. It is concluded that these RETSPLs are appropriate for electroacoustic calibration of sound field warble tones similar to those used in this study.

Reference equivalent threshold levels for pure tones and 1/3-oct noise bands: insert earphone and TDH-49 earphone.

Reference equivalent threshold sound pressure levels (RETSPLs) were determined for 20 subjects for pure tones and 1/3-oct noise bands. Two transducers were used: a Telephonics TDH-49 earphone mounted in an MX-41/AR cushion, and a Danavox SMW insert earphone coupled to an "HA-2" earmold. RETSPLs for pure tones transduced by the TDH-49 earphone were very similar to those published previously. For each transducer, RETSPLs for 1/3-oct noise bands were essentially identical to the RETSPLs for pure tones near the center of each band. Applications for threshold testing using the insert earphone and/or 1/3-oct noise bands are discussed.

Reference equivalent threshold sound pressure levels at 5 and 6.3 kHz using telephonics TDH 39 earphones with MX‐41/AR cushions

Reference equivalent threshold sound pressure levels (RETSPLs), were measured at 5 and 6.3 kHz using Telephonics TDH 39 earphones with MX‐41/AR cushions. The purpose of the test was to verify RETSPL values calculated by interpolation from those specified in present International Standards Organization acoustics standards, ISO 389 “Standard reference zero for the calibration of pure‐tone audiometers,” and its amendments. The RETSPL values are intended for the calibration of audiometers using pure tones of fixed frequencies at the preferred frequencies in one‐third octave steps or pure‐tone audiometers having a continuously variable frequency. Mean measured values of RETSPL's at 5 and 6.3 kHz were 10.9 ± 2.6 and 15.1 ± 2.4 dB, in comparison to predicted values which were 13 and 15 dB, respectively.

Real-ear calibration of ipsilateral acoustic reflex stimuli from five types of impedance meter.

The Hearing Level scale has been established in national and international standards for tones presented via supra-aural earphones. However, the standards do not encompass stimuli from the probes of ipsilateral impedance meters. This study transfers the calibration of standardised earphones to the probes of five types of impedance meter and therefore enables the intensities of their ipsilateral stimuli to be defined in terms of Hearing Levels. The method used for transfer of calibration is based on equality of acoustic reflex responses elicitied by the impedance meter probe and by a standardised earphone. Ten subjects were tested with all five instruments to ensure comparability between instruments. The resultant calibration data are expressed in terms of Reference Equivalent Threshold Sound Pressure Levels measured in both 2 cc and Zwislocki couplers. The results indicate a considerable variation amongst instruments emphasising the need for a set of calibration data for each design of probe. This variation is less marked for the Zwislock coupler than for the 2 cc coupler.

Reference Equivalent Sound Pressure Levels for Japanese Audiometric Earphones

Reference Equivalent Threshold Sound Pressure Levels (RETSPL) for 3 different types of Japanese earphone and TDH-39 earphone were determined at 8 audiometric frequencies.Alternative binaural loudness balancing was accomplished by the subject who matched the variable tone presented through the experimental earphone to one ear to the standard tone presented to the other ear three times at 30dB hearing level re ISO 389 in the WE-705A standard earphone, then the standard experimental earphones were reversed and the variable tone was matched to the standard tone.Based on mean attenuator setting of 8 subjects, RETSPLs in the NBS-9A coupler for experimental earphones were derived using B&K sound measuring system. There were found great differences in RETSPLs between earphones made in Japan and in the United States while small among the Japanese.