Trane TRG-TRC007-EN manual Loudness Contours

period two

Sound Perception and

Rating Methods

notes

Loudness Contours
	120
mPa	100
ref 20
	80
dB
pressure,	60
sound	40
	20
	0							10,000
	20	50	100	200	500	1,000 2,000	5,000
					frequency, Hz			Figure 20

The sensation of loudness is principally a function of sound pressure, however, it also depends upon frequency. As a selective sensory organ, the human ear is more sensitive to high frequencies than to low frequencies. Also, the ear’s sensitivity at a particular frequency changes with sound-pressure level. Figure 20 illustrates these traits using a set of contours. Each contour approximates an equal loudness level across the frequency range shown.

For example, a 60 dB sound at a frequency of 100 Hz is perceived by the human ear to have loudness equal to a 50 dB sound at a frequency of 1,000 Hz. Also, notice that the contours slant downward as the frequency increases from 20 to 200 Hz, indicating that our ears are less sensitive to low-frequency sounds. The contours are flatter at higher decibels (> 90 dB), indicating a more uniform response to “loud” sounds across this range of frequencies.

As you can see, the human ear does not respond in a linear manner to pressure and frequency.

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