Question

Which is the loudness level of a pure tune of 400 Hz with an SPL

of 25 dB
a) 10 phons
b) 20 phons
c) 30 phons
d) 40 phons

Answer 1

To determine the loudness in phons for a tune of 400 Hz and 25 dB SPL, you would typically refer to an equal-loudness contour chart; however, given that phon and dB are equal at 1000 Hz, the loudness at 400 Hz and 25 dB would be approximately 25 phons.

Step-by-step explanation:

The loudness level of a pure tune of 400 Hz with an SPL of 25 dB would be determined by referring to an equal-loudness contour chart, which plots the loudness in phons against the frequency in Hertz (Hz) and the Sound Pressure Level (SPL) in decibels (dB). Phons and decibels are equal at 1000 Hz; therefore, at other frequencies, the phon value must be interpolated from the chart. Since the question doesn't provide the chart, we will have to use typical values from such charts. For a frequency of 400 Hz and an SPL of 25 dB, the loudness is approximately equal to the SPL, thus it would be 25 phons, making the answer (a) 20 phons (assuming typical rounding).