In addition to Stimulus frequuncy and level, emitting Inner ear structurs status, OAEs parameters depend on conductive sound pathways charactristics, so abnormal OAEs donot always represent cochlear abnormality. Middle ear transmites Vibrations in two directions: forward and backward. Middle ear pathologies affect both forward and backward transmission.In this paper, The purpose is investigation of immediate effects of tympanic over - and under - pressure on click evoked Otoacoustic Emissions (CEOAEs) in healthy individuals. Healthy subjects with normal hearing and middle ear were exposed to ambient pressure changes in a pressure champer. The pressure was progressively changed in 100 dapa steps to accomplish on increase and decrease  in tympanic pressure. Pressure equilibration of the middle ear was avoided. The relative tympanic over-and under - pressure (+/-320 dapa) was monitored by tympanometry and CEOAEs recorded at every step of tympanic pressure change. The CEOAEs recorded during progressive tympanic over-and under- pressure had reduced amplitude and shorter latencies that were most pronounced in the 750 to 3000 Hz frequency bands.

Background and Aim: A common complaint of children with learning disability (LD) is difficulty in understanding speech in the presence of background noise. Evidence from animal and human studies has indicated that the medial olivocochlear bundle (MOCB) play a role in hearing in the presence of noise. The MOCB function can be evaluated by the suppression effect of the click evoked otoacoustic emission (CEOAEs) in response to contralateral white noise. The present study was conducted to compare the suppression effect of CEOAEs between LD and normal students.

Materials and Method: This research is an analytic-interventional study. The study group consisted of 20 learning disabled and 20 normal male students. The suppression effect of CEOAEs was evaluated by a comparison between CEOAEs levels in two conditions- with and without presentation of contralateral white noise.

Results: In the absence of noise there was no significant difference between CEOAEs amplitudes of two groups while there was significant difference between CEOAEs of two groups in the presence of noise. The suppression effect of CEOAEs in normal students had significant difference with LD students.

Conclusion: The reduced suppression effect in LD students indicates the reduced activity of the MOCB function and efferent pathway in LD students which affect their ability to hear in the presence of background noise. Consequently, the suppression effect of CEOAEs can be used in the test battery approach of LD children.

Background and Aim: Vestibular evoked myogenic potential (VEMPs) is one of the clinical tools to evaluate vestibular function. The VEMPs can be recorded from sternocleidomastoid muscle by auditory stimulation with various sound stimuli and are thought to have saccular origin. The aim of this study was to compare the VEMP responses evoked by short (500 Hz) tone burst (STB) with those evoked by click stimuli in healthy young individuals.          

Materials and Methods: Thirty healthy volunteers (15 males, 15 females) with ages of 18 to 30 years were enrolled in this study. Subjects were instructed to sit on a chair and rotate their head to the opposite side of the recording muscle. The VEMPs was recorded using 500 Hz STB and then click sound stimuli to each ear. The p13 and n23 latencies, p13-n23 peak-to-peak amplitude and VEMPs thresholds were obtained for further analysis.       

Results: The VEMP responses were present in all subjects for STB and ware not recorded in one subject for click. The latencies of p13 and n23 of STB-VEMP were significantly longer, and the p13- n23 amplitudes were significantly greater for STB-VEMP (p<0.05), and thresholds were higher for clicks (p < 0.05). No significant difference was obtained between both ears and genders. (p > 0.05).

Conclusion: The VEMP responses were significantly different between the stimuli of STB and click, and the norms of different stimuli should be established for clinical interpretations. According to these data, we recommend STB stimuli in comparison with clicks for clinical diagnosis.

Background and Aim: It is not known how electrocochleography components of action potentials (AP) and summating potentials (SP) are changed in response to CE-chirp stimulus using extra-tympanic electrodes. This study was done for comparing summating potentials and action potentials specifications in response to CE-chirp and click stimuli.

Methods: Electrocochleography components of action potentials and summating potentials were recorded in 16 normal hearing subjects (8 men and 8 women) aged 22-30 years (mean: 26.7 with SD 2.5 years) with audiometric (250-8000 Hz) hearing thresholds of 15 dB HL or better in response to click and CE-chirp stimulus at 90 dB nHL. Amplitude, duration, latency and area of summating potentials and action potentials and SP/AP amplitude and area ratios were compared.

Results: Among the measured parameters, action potentials amplitude in response to CE-chirp stimulus (0.41 with SD 0.26 µV ) was significantly smaller than action potentials amplitude in response to click (0.61 with SD 0.29 µV ) stimulus (p<0.005). Relative frequency of detecting summating potentials in response to CE-chirp (68.7%) was lower than (100%) click (p<0.005).

Conclusion: Recording electrocochleography component of summating potentials and action potentials with CE-chirp stimulus at high intensity level in normal hearing individuals shows no advantage over click stimulus. Small amplitude of summating potentials as a major problem of extra-tympanic electrocochleography cannot be solved using CE-chirp stimulus.

Background and Aim: CE-Chirp stimulus has been developed for stimulating more apical regions of the cochlea. Inadequacy of clinical information on the latency and amplitude characteristics of ABR evoked by CE-chirp at different levels in addition to discrepancy in identifying earlier ABR waveforms using CE-chirp stimulus are the reasons of this study.

Methods: This study was done by recoding ABR to click and broad-band CE-chirp stimuli in the right ear of 15 non-randomly selected normal-hearing individuals with age range of 20-30 years old. Frequency of recordable waves I and III, as well as threshold, amplitude, and latency of wave V were compared in response to click and CE-Chirp at 20-80 dB nHL.

Results: At 80 dB nHL, click stimulus evokes waves I and III more frequently than chirp stimulus (p=0.012 and p=0.016 respectively). At 20 and 40 dB nHL, wave V latency evoked by CE-Chirp is significantly longer than wave V latency evoked by click (p=0.012 and p=0.0001 respectively) however, at 80 dB nHL wave V latency evoked by CE-Chirp is shorter than click (p=0.0001). Wave V amplitude for CE-Chirp is significantly larger than for click at levels of 20, 40 and 60 dB nHL (p=0.0001, p=0.0001 and p=0.013 respectively). Wave V threshold is approximately 5 dB lower with CE-chirp compared to click (p=0.014).

Conclusion: Except at high levels, CE-Chirp evokes wave V with larger amplitude and lower threshold than click. Possibility of recording earlier ABR waves is reduced with CE-chirp stimulus.