The Resonance Frequency of the External Auditory Canal in Children

Abstract

The frequency of the resonance peak of the external auditory canal was measured in 250 children aged 3 to 12 years. The mean resonance peak frequency was greatest in the younger age groups (3089 Hz in 4 year olds, range 2298 to 3763) and then decreased with age until 7, the age at which adult values were reached. Children less than 7 years of age have mean resonance frequencies significantly different from adults, suggesting that the "adult" length of external auditory canal is not reached until the age of 7. This alteration in resonance frequency with age may have practical implications by affecting the insertion gain of hearing aid systems in children.THE EXTERNAL AUDITORY CANAL, by virtue of being a blind ended cylinder, increases the sound pressure at the tympanic membrane relative to that of the external field. The magnitude of this amplification peaks at a specific frequency, the resonance frequency. As the resonance frequency of any tube is inversely related to its length, it might be expected that the resonance frequency of the external auditory canal would be at its highest in neonates, thereafter progressively reducing with age until the adult level is reached. Indeed, Kruger (1987) and Kruger and Ruben (1987) have reported that the resonance frequency in neonates approached 7000 Hz with the adult value of around 2700 Hz being reached by the age of 3 years. However, clinical observation would suggest that a 3-year-old child does not have an external auditory canal of adult size and, by implication, a n adult resonance frequency. The potential clinical relevance of the relationship between resonance frequency and age is in the provision of hearing aids. First, there is evidence that a reduction in canal length, with a resultant reduction in external auditory canal volume, will lead to an increase in the insertion gain. Second, occlusion of the external auditory canal with a mold will lead to loss of the open ear resonance frequency, with loss of the selective amplification at this frequency. The aim of this study was to evaluate the frequency of the resonance peak of children 3 years of age and over and to assess the age at which adult values are achieved. METHODWe studied 250 children, aged 3 to 12 years (mean, 6.25), who were referred to Glasgow Royal Infirmary for management of various otolaryngological symptoms. Sixty percent of these children were being monitored for the presence of otitis media with effusion. All children were within normal limits for height, weight, and head circumference and had no gross deformity of the external ear. Following otoscopy to ensure that the canal was free from occlusive wax, the resonance characteristics of the external auditory canal were measured in an anechoic room using the Rastronics CCl-10 frequency response analyzer. Calibration for the acoustics of the test room was performed by placing the probe microphone 0.5 m from the free-field sound source and sweeping through the frequency range 250 to 8000 Hz. The children were then seated in a chair 1 m from the s...

Measurement of the sound intensity during suction of middle-ear fluid following myringotomy

“…The damage is usually seen in the 3-5 kHz range with the characteristic 4 kHz downward notch related to the resonance of the external auditory canal. 8 Temporary threshold shifts are reversible hearing losses; the outer hair cells have the ability to repair the damage, with resolution in 24 to 48 hours. 4 Permanent threshold shifts are more severe, with irreversible damage within the cochlea.…”

Alternative Metrics for Real-Ear-to-Coupler Difference Average Values in Children

“…Selection of these constant insertion depths was based on the work of Feigin et al (1989), who used an insertion depth of 10 mm for children and 15 mm for adults. Our use of a 15 mm insertion depth for ages older than 7 yr was based on the work of Dempster and Mackenzie (1990), who reported that canal length and resonant frequency reach adult values at age 7 yr. The E•A•R-Tone ER-3A insert earphone (10 ohms) cable assembly was inserted into an auxiliary speaker jack of RM500 equipment.…”

Untersuchung über Korrelation von Gehörgangsresonanz und Trommelfellimpedanz bezüglich Alter und Körpermaßen sowie Veränderungen nach Todeseintritt

“…Das Absinken der Resonanzfrequenz mit zunehmendem Alter ist mehrfach beschrieben. Der Erwachsenenwert von 2750 Hz wird nach Kruger [15] mit 2, nach Demster und MacKenzie [4] mit 7 Jahren erreicht.…”