Frequency resolving power measured by rippled noise

Frequency resolving power (FRP) was measured in normal humans using rippled noise with a phase-reversal test. The principle of the test was to find the highest ripple density at which an interchange of mutual peak and trough position (the phase reversal) in the rippled spectrum is detectable. In the frequency range below 0.5 kHz FRP was found to be about 21 ripples per kHz when tested by both broad-band and narrow-band rippled noise. In the frequency range above 2 kHz, FRP measured by the narrow-band rippled noise was 22 to 23 relative units (relation of the noise central frequency to the ripple frequency spacing).