Characteristics of the 2f1-f2 distortion product otoacoustic emission in a normal hearing population

Abstract

Distortion-product otoacoustic emission (DPOAE) fine structure and component characteristics are reported between 0.75 and 16 kHz in 356 clinically normal hearing human subjects ages 10 to 65 yr. Stimulus tones at 55/40, 65/55, and 75/75 dB SPL were delivered using custom designed drivers and a calibration method that compensated for the depth of insertion of the otoacoustic emission (OAE) probe in the ear canal. DPOAE fine structure depth and spacing were found to be consistent with previous reports with depth varying between 3 and 7 dB and average spacing ratios (f/Δf) between 15 and 25 depending on stimulus level and frequency. In general, fine structure depth increased with increasing frequency, likely due to a diminishing difference between DPOAE component levels. Fine structure spacing became wider with increasing age above 8 kHz. DPOAE components were extracted using the inverse fast Fourier transform method, adhering to a strict signal to noise ratio criterion for clearer interpretation. Component data from four age groups between 18 and 55 yr old were available for the stimulus levels of 75/75 dB SPL. The age groups could be differentiated with greater than 90% accuracy when using the level of the component presumed to originate from the DPOAE characteristic frequency place. This accuracy held even for frequencies at and below 4 kHz where the age groups exhibited similar average hearing thresholds.

Acquisition and Repeatability of High-Frequency Distortion Product Otoacoustic Emissions Using Two Different Calibration Methods in Newborns

“…DPOAEs up to 16 kHz are measurable in some newborns and the average DPOAE levels are comparable across frequencies for both calibration methods and trials and decline at frequencies greater than 8 kHz ( Figure 2). Declining DPOAE levels as frequency is increased have been reported previously in term newborns, children, and adults [5,7,8,[48][49][50]52]. Unlike previous studies which measured DPOAEs out to 16 kHz and demonstrated the largest DPOAE levels occurring around 4-5 kHz in children (≥3 years) and adults [5,[48][49][50]52], the newborns in this study showed a peak DPOAE level at 8 kHz.…”

“…Previously, HF (up to 16 kHz) DPOAEs have been measured in normal-hearing children [48,49,52] and young adults [5,48,50,78]. However, DPOAE levels are reduced at higher frequencies compared to conventional frequencies and are not always present for every individual at the highest frequencies tested [5,48,50,78]. Newborns compared to children and adults have different ear canal and middle ear characteristics [8,15], which can influence DPOAE measures.…”

“…Ideally, cochlear health would be monitored at the highest frequencies producing a response as this is where damage initially occurs due to ototoxic drug exposures [47]. Using customized equipment, HF (up to 16 kHz) DPOAEs have been measured [5,48] and are repeatable across testing sessions in normal-hearing young adults and children [5,[49][50][51][52], in those with cystic fibrosis tested between ototoxic treatments [51], and identified the earliest signs of damage at the highest frequencies with present DPOAEs in adults exposed to ototoxic agents [53], but have not been recorded in newborns. While DPOAEs may not be recorded at the highest frequencies of human hearing for each individual based on their cochlear health, it is imperative to monitor the highest frequencies with a response in individuals exposed to ototoxic agents to identify the earliest signs of damage [53,54].…”

Compensating for ear-canal acoustics when measuring otoacoustic emissions

“…Recordings of otoacoustic emissions (OAEs) offer a noninvasive means of monitoring and assessing the health of the cochlea's outer hair cells and related aspects of inner-ear mechanics. For example, because emission levels tend to fluctuate before significant changes in hearing sensitivity appear, OAEs provide a harbinger of impending sensory hearing loss due to sound exposure, ototoxic drugs, and aging (Ahmed et al, 2001;Campbell, 2004;Lapsley Miller and Marshall, 2007;Marshall et al, 2009;Rao and Long, 2011;Poling et al, 2014). Because basal regions of the cochlea are the most susceptible to damage, OAE changes are often first observed and most prominent at high frequencies.…”

Revisiting Oto-Acoustic Emissions

“…It is well known that signs of aging are evident at higher frequencies. However, new findings have demonstrated that signs of aging are visible in DPOAE levels at frequencies as low as 1000 Hz for individuals as young as 20 years old 38 . This forces us to change our perception about auditory aging and when might be the right time to start awareness campaigns to protect our ears.…”