Phase spectral analysis as developed by Fridman (1982) was used to det
ect amplitude-modulation following response (AMFR). The threshold of A
MFR was determined with greater sensitivity and accuracy by phase spec
tral analysis than by visual analysis. Using this method, a modulation
frequency (MF) of 80 Hz was found optimal for detecting AMFR in young
children (ranging in age from 2 to 4 years) during sleep, for whom th
ere is no advantage in recording 40-Hz steady-state response. To deter
mine the optimal MF for detecting AMFR during sleep in children less t
han 2 years of age and age limitation for using 80-Hz MAFR in objectiv
e audiometry, AMFR as a function of MF was investigated during sleep i
n 25 children with normal hearing ranging from 4 months to 15 years of
age, and 10 normal hearing adults. The stimulus was a 1000 Hz, 50 dBn
HL sinusoidally amplitude modulated tone with a modulation depth of 95
%. MF was varied from 20 to 200 Hz in 20 Hz steps. Response was determ
ined by phase spectral analysis and the S/N ratio calculated by spectr
al amplitude at the modulation frequency and noise level around the mo
dulation frequency using fast Fourier transform. Phase spectral analys
is showed AMFR at MF of 80 Hz to be the most stable and reliable in al
l children during sleep among MFs from 20 to 200 Hz. Spectral amplitud
e analysis demonstrated 80-Hz AMFR to have a high S/N ratio in all chi
ldren. 80-Hz AMFR would thus appear to be useful for assessing hearing
even in infants and children in their early teens, though it is not a
dequate for hearing assessment in adults.