Two-tone maskers define critical bandwidth at the threshold’s transition point.

Evidence

Masking in frequency gaps is the second method used in determining critical bandwidth. A relatively simple combination of masker and test sound involves the use of two tones of equal level as masker, and a narrow-band noise as the test sound. The threshold of the test sound masked by the two tones is measured as a function of the frequency separation between the two masker tones with the narrow-band noise centred between them. The bandwidth of the test sound has to be small in relation to the expected critical bandwidth. The inset in Fig. 6.3 shows the frequency composition, and Fig. 6.3 shows the data that are produced by two 50-dB tone maskers and a narrow-band noise centered at 2 kHz. The threshold of the narrowband noise masked by the two tones is plotted as a function of the frequency separation between the two tones. For narrow frequency separations, L1j, the masked threshold remains independent of L1j. Beyond a certain L1j, called the critical bandwidth, threshold decreases. — Professor Dr.-Ing. Hugo Fastl, Professor Dr.-Ing. Eberhard, Psychoacoustics- Facts and Models, 890

Categorization

• DEFINE: Explains the ‘masking in frequency gaps’ method, where the critical bandwidth is operationally defined as the crossing point where masked threshold begins to decay.