Chapter 7: Loudness and Pitch

Loudness (1) Auditory Sensitivity: Minimum audible pressure (MAP) and Minimum audible field (MAF) Equal loudness contours (Fig. 7-1) Phon: basic measure of loudness; the loudness of a 1000 Hz pure tone at 40 dB SPL is designated as 40 phons 55 dB SPL at 100 Hz= 40 dB SPL at 1000 Hz (40 phons) At low levels, the differences between the physical measurement in dB and the loudness level in phons is very large.

Loudness (2) Phon: indicates that two sounds are different in loudness Sone scale: loudness measurement in which 1 sone equals 40 phons and 2 sone is twice as loud as 1 sone. Sone components: (1)Magnitude estimation: estimate the loudness magnitude of various levels of stimuli presented (2)Magnitude production: adjust the level of the stimuli to be twice as loud, half as loud, and so on, relative to the reference 40-phon (1-sone) stimulus

Loudness (3) Advantages of the sone scale: It tells us not only that 2 sones is louder than 1 sone, but also that 2 sones is twice as loud as 1 sone, that 4 sones is twice as loud as 2 sones, and so on (Fig.7-2). A change of 10 dB results in a doubling or halving of perceived loudness The phon: ordinary scale while the sone is interval scale For noise-band stimuli, the loudness of a sound at a fixed overall sound pressure level (OASPL) increases when the band-width of the noise is expanded to the point that it exceeds the critical band

Loudness (4) Other perceived qualities of sound: noisiness and annoyance values dependent on spectral distribution, duration, intermittency, variability of intensity and frequency Loudness: the subjective perception of the intensity of a sound.

Pitch (1) Pitch: the psychological perception of the physical property of frequency Ordinarily, the higher the frequency of an auditory signal, the higher will be the perceived pitch. Quantification of the sensation of pitch: (1)fractionalization: a subject was presented with a tone and was asked to adjust the frequency of a second tone until it was perceived as half the pitch of the first tone, one-third the pitch of the first tone, and so on (2)Ask subjects to adjust the frequencies of five tones until they were equally different in pitch

Pitch (2) Mel scale: psychological measure of pitch; the pitch of a 1000 Hz tone at 40 dB SPL is 1000 mels. Mel scale: an interval scale quantifying the difference in pitch Difference tone: low frequency tone perceived by a listener with a frequency that the difference between two tones presented at a high intensity level, even though no acoustic energy is present at that frequency, 2F1-f2, f1-f2 Summation tone: high frequency tone perceived by a listener with a frequency that is the sum of two tones presented at a high intensity level, even though no acoustic energy is present at that frequency, f1+f2