Simultaneous masking raises a test tone’s just-audible level above threshold in quiet.

Evidence

There are two ways of overcoming this phenomenon of masking. We can either wait until the truck passed and then continue our conversation, or we can raise our voice to produce more speech power and greater loudness. Our partner then can hear the speech sound again. Similar effects take place in most pieces of music. One instrument may be masked by another if one of them produces high levels while the other remains faint. If the loud instrument pauses, the faint one becomes audible again. These are typical examples of simultaneous masking. To measure the effect of masking quantitatively, the masked threshold is usually determined. The masked threshold is the sound pressure level of a test sound (usually a sinusoidal test tone), necessary to be just audible in the presence of a masker. Masked threshold, in all but a very few special cases, always lies above threshold in quiet; it is identical with threshold in quiet when the frequencies of the masker and the test sound are very different. — Professor Dr.-Ing. Hugo Fastl, Professor Dr.-Ing. Eberhard, Psychoacoustics- Facts and Models, 397

Categorization

• DEFINE: Defines ‘masked threshold’ — the sound pressure level at which a test sound becomes just audible in the presence of a masker.