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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
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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: • Magnitude estimation: estimate the loudness magnitude of various levels of stimuli presented • 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: • 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 • 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