Equivalent threshold sound pressure levels (ETSPLs) for Oscilla H210A circumaural audiometric headphones.

OBJECTIVE: To determine ETSPLs for the Oscilla H210A circumaural audiometric headphones. DESIGN: ETSPL measurements were performed for 11 audiometric frequencies with the ISO 8253-1 (2010) bracketing procedure. STUDY SAMPLE: The study was based on 25 otologically normal test subjects. RESULTS: ETSPLs are provided for an ear simulator according to IEC 60318-1 (2009) along with a detailed measurement uncertainty budget. CONCLUSIONS: ETSPLs for the Oscilla H210A headphones may be used to update ISO 389-8 (2004), the reference ETSPL standard for circumaural audiometric headphones.

Influence of response-time limits on automated hearing threshold determination.

OBJECTIVE: In automated hearing threshold determination procedures, prespecified response- time limits can be applied to evaluate whether a stimulus was truly heard by checking whether the test subject reacts to the onset and the offset of the stimuli within given time intervals. The influence of different response-time limits on the threshold of normal-hearing test subjects was investigated. DESIGN: Two-stage hearing threshold level measurements applying the ISO 8253-1 (2010) bracketing procedure were performed. Pre-tests at 125 Hz and 1000 Hz were carried out with maximum accepted response times of 600 ms, 1000 ms, and 1200 ms. Subsequently, thresholds were measured at the seven octaves between 125 Hz and 8000 Hz with maximum accepted response times of 600 ms and 1000 ms. STUDY SAMPLE: 15 test subjects in pre-tests, 25 test subjects in the main study. RESULTS: Threshold levels determined with a maximum accepted response time of 1000 ms are 2.6 dB lower than those obtained with a maximum accepted response time of 600 ms (95% CI -1.6 dB to 6.9 dB). The threshold shift was similar at all frequencies. CONCLUSIONS: Based on this study, response-time limits after both stimulus onset and offset of at least 1000 ms are recommended.

Temporal integration of infrasound at threshold.

Infrasounds are signals with frequencies below the classical audio-frequency range, i.e., below 20 Hz. Several previous studies have shown that infrasound is audible as well, provided that the sound level is high enough. Hence, the sound pressure levels at threshold are much higher than those in the classical audio-frequency range. The present study investigates how the duration and the shape of the temporal envelope affect thresholds of infrasound stimuli in quiet. Two envelope types were considered: one where the duration of the steady state was varied (plateau bursts) and one where the number of consecutive onset-offset bursts was varied (multiple bursts). Stimuli were presented monaurally to human listeners by means of a low-distortion sound reproduction system. For both envelope types, thresholds decrease with increasing duration, a phenomenon often referred to as temporal integration. At the same duration, thresholds for plateau-burst stimuli are typically lower than those for multiple-burst stimuli. The data are well described by a slightly modified version of a model that was previously developed to account for temporal integration in the classical audio-frequency range. The results suggest similar mechanisms underlying the detection of stimuli with frequencies in the infrasound and in the classical audio-frequency range. Since the model accounts for the effect of duration and, more generally, the shape of the envelope, it can be used to enhance the comparability of existing and future datasets of thresholds for infrasounds with different temporal stimulus parameters.

Spectral integration of infrasound at threshold.

The present study investigated the effect of the number of spectral components on the threshold in quiet of infrasound stimuli. Stimuli with one, two, or three sinusoidal components were presented monaurally to the ear with a low-distortion infrasound reproduction system. All components of the complex tones had the same level relative to their respective pure-tone threshold. The data are consistent with the assumption of a (perceptually weighted) intensity integration at threshold: The level at threshold for each component is 3 dB lower when two components were presented simultaneously. Thresholds decrease further, when a three-tone complex is used.

Equivalent threshold sound pressure levels (ETSPLs) for RadioEar DD65v2 circumaural audiometric headphones.

Objective: Equivalent threshold sound pressure levels (ETSPLs) were determined for RadioEar DD65v2 audiometric headphones.Design: The pure-tone hearing threshold levels were measured for 11 audiometric frequencies between 0.125 and 8 kHz, according to the conditions specified in ISO 389-9. ETSPLs are provided for an ear simulator according to IEC 60318-1, complemented by a comprehensive uncertainty budget.Study sample: The study was based on 25 otologically normal test subjects.Results: ETSPL values are provided with expanded measurement uncertainty. The data are compared for left/right ears as well as male/female test subjects.Conclusions: The results of both studies may be used to update ISO 389-8, the RETSPL standard for circumaural audiometric headphones.

Equivalent hearing threshold levels for the RadioEar IP30 insert earphone and short-term stimuli: comparison of peak-equivalent and RMS-based measures.

Objective: To determine equivalent threshold sound pressure levels (ETSPL) for the RadioEar IP30 insert earphone for standardised short-term stimuli: IEC 60645-3 reference clicks and tonebursts in the frequency range from 250 Hz to 6 kHz, using the standardised peak-equivalent ETSPL procedure (peETSPL) and a new proposal based on the unweighted equivalent continuous sound pressure level LZeq. of the periodically repeated short-term stimuli (LZeqETSPL).Design: Determination of peETSPL and LZeqETSPL hearing threshold levels with otologically normal test subjects under the conditions given in ISO 389-9 using the standardised occluded-ear simulator according to IEC 60318-4.Study sample: The study was based on tests with 25 subjects.Results: The peETSPLs for the RadioEar IP30 insert earphone were compared with the respective reference threshold levels of the insert earphone ER-3A as standardised in the ISO 389 standards series. The LZeqETSPL approach was tested by estimating the LZeqETSPLs from the peRETSPLs and comparing the estimate with the direct results.Conclusions: Equivalent hearing threshold levels for standardised short-term stimuli for the RadioEar IP30 insert earphone were determined according to ISO 389-9 and given as both peETPSL and LZeqETSPL. The RMS-based LZeqETSPL approach turned out to be well applicable for the RadioEar IP30 insert earphone.

Infrasonic and low-frequency insert earphone hearing threshold.

Low-frequency and infrasonic pure-tone monaural hearing threshold data down to 2.5 Hz are presented. These measurements were made by means of a newly developed insert-earphone source. The source is able to generate pure-tone sound pressure levels up to 130 dB between 2 and 250 Hz with very low harmonic distortions. Behavioral hearing thresholds were determined in the frequency range from 2.5 to 125 Hz for 18 otologically normal test persons. The median hearing thresholds are comparable to values given in the literature. They are intended for stimulus calibration in subsequent brain imaging investigations.

Distortion product otoacoustic emissions upon ear canal pressurization.

The purpose of this study was to quantify the change in distortion product otoacoustic emission (DPOAE) level upon ear canal pressurization. DPOAEs were measured on 12 normal-hearing human subjects for ear canal static pressures between -200 and +200 daPa in (50 ± 5) daPa steps. A clear dependence of DPOAE levels on the pressure was observed, with levels being highest at the maximum compliance of the middle ear, and decreasing on average by 2.3 dB per 50 daPa for lower and higher pressures. Ear canal pressurization can serve as a tool for improving the detectability of DPOAEs in the case of middle-ear dysfunction.

How the cross-sectional discontinuity between ear canal and probe affects the ear canal length estimation.

Many ear canal probes both deliver and measure sound via narrow tubes. This study investigates the effect of the cross-sectional discontinuity at the interface between ear canal models and the connecting tubes of a commercially available otoacoustic emission probe on the "acoustically" estimated cavity lengths. Rigid cavities having the same length but different diameters were produced, and modeled by the finite element method. Cavities with a diameter larger than 8 mm had acoustic lengths that considerably overestimated the real geometry. A length correction was derived, which, in most applications, compensates for the measurement errors emerging from the discontinuity effects.

Equivalent hearing threshold levels for the Etymotic Research ER-10C otoacoustic emission probe.

OBJECTIVE: To determine the equivalent threshold sound pressure levels (ETSPL) for a commercially available distortion product otoacoustic emission (DPOAE) probe, and to study the impact of probe fitting and eartip size on the calibration. DESIGN: Twenty-eight otologically normal test subjects participated in the ETSPL determination for the Etymotic Research ER-10C probe. STUDY SAMPLE: ETSPLs were determined up to 16 kHz and were compared to the reference hearing thresholds associated with the ER-3A insert earphone. Both 'regular' and 'baby' foam eartips were used. RESULTS: At most frequencies, no significant threshold differences were observed between the insert earphone and the DPOAE probe. However, at 1 kHz and 4 kHz, the mean thresholds for the insert earphone were generally lower than those for the DPOAE probe, suggesting systematic differences at those frequencies. Repeated calibration runs resulted in deviations of about 0.6 dB. Similar deviations were noticed when using foam eartips of different sizes up to 10 kHz. CONCLUSIONS: Knowing the reference thresholds for DPOAE probes enables measurements of (subjective) hearing thresholds and (objective) otoacoustic emissions using the same probe. Probe fitting and eartip size had negligible effect on the determination of ETSPLs. The obtained data may be proposed for inclusion in future audiometry standards.

Reference zero for the calibration of air-conduction audiometric equipment using 'tone bursts' as test signals.

The aim of this study was to determine reference peak-to-peak threshold sound pressure levels for air conduction sound transducers using groups of tone bursts as test signals. For this purpose, threshold measurements with five different earphones and a loudspeaker were carried out on groups of 25 young, otologically normal test subjects in the frequency range between 250 Hz and 8000 Hz, following as closely as possible the ISO Preferred Test Conditions. The dependence of the results on repetition rate, type of sound transducer, gender and age of the test subjects, and on reference pure tone thresholds was investigated. The results mainly depend on the reference equivalent sound pressure levels for pure tones of each sound transducer. Together with the results of another study carried out in Denmark, the data of the present study will form the basis for the International Standard ISO 389 Part 6 on reference hearing thresholds for acoustic test signals of short duration.

Reference zero for the calibration of audiometric equipment using 'clicks' as test signals.

Intended as an input to international standardisation, this study investigated reference hearing thresholds for the calibration of audiometric equipment, which have been determined using 'clicks' as test signals, several kinds of earphones, and two types of transducers (a loudspeaker and a bone vibrator). The threshold measurements were carried out with groups of 25 test persons with normal hearing capability following as far as possible the ISO-preferred test conditions. The influence of different parameters on the results, such as click duration, polarisation mode, repetition rate, gender and age of the test persons, or type of ear simulator, was studied. The results mainly depend on the type of ear simulator used to calibrate corresponding audiometers. Together with the results of another investigation carried out in Denmark, the data of the present study shall form the basis for the coming International Standard ISO 389-6 on reference hearing thresholds for acoustic test signals of short duration.

Determination of the acoustic output of a harmonic scalpel.

The acoustic output of a harmonic scalpel was experimentally determined, and both the airborne ultrasound and the ultrasound transmitted in water were taken into account. The sound pressure level of airborne ultrasound was measured with a microphone and an artificial head, so that the free-field value and the sound level at the entrance at the bottom of the cavum conchae of the ear could be determined. The derived output power in water was obtained from a hydrophone measurement. The results were strongly influenced by cavitation effects, and it is shown that the power values with and without cavitation differ by more than a factor of 5. The measurement of acoustic output parameters forms the basis for describing the performance of the devices and for an assessment of the risk of harmful bioeffects on both the operator and the patient.