# Short-term impact of preschool sound exposure on outer hair cell function in young children: An analysis using pressurised distortion product otoacoustic emissions

## TL;DR

This study investigates whether preschool noise exposure affects hearing in young children using a specific hearing test, but finds no direct link between noise and hearing function.

## Contribution

The study introduces pressurized distortion product otoacoustic emissions to assess cochlear function in preschool children, accounting for middle-ear pressure.

## Key findings

- No significant association was found between preschool noise exposure and pressurized DPOAE amplitudes.
- DPOAE amplitudes varied by time of day and sex, with higher values observed in the afternoon and in girls.
- Most preschool noise levels were within typical ranges, but some exceeded 115 dB.

## Abstract

Preschool children are regularly exposed to high noise levels that may affect hearing. A previous study has linked preschool noise exposure to reduced distortion product otoacoustic emission (DPOAE) amplitudes. Since DPOAEs primarily reflect outer hair cell (OHC) activity, they provide an indirect marker of cochlear function. Measurement accuracy can be affected by middle-ear pressure. Pressurised DPOAEs (pDPOAEs) compensate for middle-ear pressure during recording.

This cross-sectional study aimed to examine the relationship between preschool noise exposure and pDPOAE amplitudes while accounting for middle-ear pressure. Seventy-five children (4–6 years old) were monitored using dosimeters to measure the equivalent continuous sound level (LAeqTi) and the 95th percentile of maximum levels (LAFmax,95). Of these, 56 children completed pDPOAE testing at four time points during the preschool week. Linear mixed-effects models evaluated associations with noise exposure, time of day and progression across the week.

For personal dosimetry, the mean LAeqTi was 80 dB (range: 60–98 dB) and the mean LAFmax,95 was 97 dB (range: 77–110 dB). Most LAeqTi levels (86.2%) were between 75–85 dB, with LAFmax levels exceeding 115 dB in 53.8% of the cases. No significant associations were found between LAeqTi or LAFmax,95 and pDPOAE amplitudes (p > 0.05). Time-of-day differences were observed, with higher amplitudes in the afternoon at 4 kHz (p = 0.045) and 6 kHz (p = 0.047) in the right ear, and 3 kHz in the left ear (p = 0.021). Girls showed higher amplitudes than boys at 4 kHz in the left ear (p = 0.030).

Although pDPOAE amplitudes varied with time of day, and sex, a direct exposure–response relationship with preschool noise was not demonstrated. Short-term variations in typical preschool noise exposure may not measurably affect cochlear function in young children. Future research should refine exposure assessment and recording protocols to reduce variability and improve detection of small physiological changes.