The Relationship between the Change of Otoacoustic Emission and Temporary Threshold Shift after Broad Band Noise Stimulation

Abstract

Background and ObjectivesZZA distortion product otoacoustic emission (DPOAE) is a noninvasive method which is commonly used to assess the hearing function of the cochlea and to reflect objective information of specific frequency in the cochlea. We hypothesize that after applying a broad band noise (BBN), the outer hair cell’s function will change and cause reduction in the amplitude of DPOAEs and signal to noise ratio (SNR). Subjects and MethodZZWe performed the examination on 40 subjects (80 ears) who have a normal hearing function. DPOAEs were recorded before and after BBN stimulation (intensity: 90 dB HL, duration: 10 minutes). ResultsZZAfter the BBN stimulation, the amplitude of DPOAEs and SNR were decreased at all frequencies. The amplitude of DPOAEs and SNR decreased 0.3-1.6 dB SPL, 0.6-1.5 dB SPL, respectively. Decreases in the amplitude had statistical significances after 3 and 6 minutes in 1 kHz, 3 and 6 minutes in 2 kHz, immediately after noise exposure, and after 3 and 6 minutes in 6 kHz. However, the SNR changes had statistical significance only after 3 minutes in 1 kHz. After the stimulation, pure tone threshold at 4 kHz increased 3.2±3.9 dB HL. After the BBN exposure, the amplitude of DPOAEs and SNR decreased at all frequencies and most of them recovered within 12 minutes. ConclusionZZThese results suggest that DPOAE could be a clinically useful method for the purpose of screening, managing and assessing the prognosis of acoustic trauma and noise induced sensorineural hearing loss. Korean J Otorhinolaryngol-Head Neck Surg 2010;53:143-7 Key WordsZZOtoacoustic emissions·Noise·Auditory fatigue.