Masking

The process by which the threshold of audibility for one sound is raised by the presence of another. Signal = sound of interest (Tone A), Masker = the interfering sound

Partial masking: the reduction in loudness that can occur when a second sound is presented

Threshold for tone A= 1kHZ at 5 dB SPL Sound B is introduced and the threshold for Tone A is measured in the presence of Sound B. The new tone A threshold = 15 dB SPL( a.k.a, the masked threshold). Threshold for Tone A increased given that there was a decrease in sensitivity to Tone A

Tonal masking: the masker is a tone -Effective maskers are at frequencies that are close to the center frequency of the signal. The greater the frequency difference between the signal and the masker, the greater the intensity of the masker must be to mask effectively. Tonal Masking: Intensity- Masking increases as the intensity of the masker is raised

the masker is some type of noise

Masker tones that are lower than the signal frequency do a better job of masking the signal Masker tones that are higher than the signal frequency are less effective. Thus, a masker of a given frequency masks higher frequency signals more than lower frequency signals which is called “upward spread of masking” When signal and masker are very close in frequency, you get beats

when you combine a very large number of pure tones, where the individual frequencies do not share a mathematical relationship.

Less easily confused with pure tone signal and doesn’t cause beats. As the spectrum level of white noise is raised, overall threshold for signal detection rise

White noise (White Band Noise)- contains a wide range of frequencies thus it masks tones of many different frequencies. Narrow band noise:- Noise is specifically centered on frequency of signal of interest

Signal and masker are presented at the same time, tone on tone and noise on tone

Time- signal and masker need to be presented within less than 50-100 ms of each other to show masking effects.

Forward Masking: Masker occurs before signal Backward Masking: Masker occurs after the signal Simultaneous Masking: Masker and the signal occur at the same time, or the signal is temporally presented in the middle of the masker.