Low-frequency otoacoustic emissions in schoolchildren measured by two commercial devices

Abstract

ObjectiveClick evoked otoacoustic emissions in children are known to be good indicators of hearing function when used in the frequency range 1.5–4kHz. Using two commercial devices, the present study investigates the usefulness of responses in the lower frequency range of 0.5–1kHz evoked by 0.5kHz tone bursts. MethodsOtoacoustic emissions (OAEs) were recorded from the ears of 37 schoolchildren (age 12–13 years). OAE measurements were then made using two devices: the ILO 292 (Otodynamics) and the HearId (Mimosa Acoustics). Each device was used for two measurements: first with a standard click stimulus at 80dB pSPL (CEOAEs) and a second using a 0.5kHz tone burst at 80dB pSPL (TBOAEs). Pure tone audiometry and tympanometry were also conducted. Half-octave-band values of OAE signal to noise ratios (SNRs) and response levels were used to assess statistical differences. ResultsBoth devices provided similar SNR results for click and tone burst stimuli, although the ILO device generated slightly higher response levels for clicks. For the 0.5kHz tone bursts, both devices evoked very weak responses at 0.5kHz and the peak response occurred at 0.7–1kHz. Generally, CEOAE SNRs were about 10dB in the 1–4kHz range, while SNRs for 0.5kHz TBOAEs were about 10dB at 0.7–1kHz. Conclusions0.5kHz TBOAEs could be measured in children as effectively as CEOAEs. They can provide additional information about the 0.7–1kHz frequency range, a range over which CEOAEs do not usually contain responses above the noise floor. The main difficulty was that the maxima of the 0.5kHz TBOAEs occurred at frequencies of 0.7–1kHz, probably because of spectral splatter from the short tone burst stimulus and from rapidly falling responses of the cochlea and the recording system at low frequencies.