Question

What sound intensity levels (in dB) must sounds of frequencies 60, 100, and 800 Hz have in order to have the same loudness as a 40 dB sound of frequency 1000 Hz (that is, to have a loudness of 40 phons)?

Answer 1

Answer:

For 60 Hz, the intensity should be 60 dB

For 100 Hz, the intensity should be 50 dB

For 800 Hz, the intensity should be approximately 38 dB

Explanation:

To understand what the sound intensity levels should be in order for each sound at different frequencies to be perceived as equally loud, we can make use of a helpful graph known as the Fletcher-Munson curve. For reference, the graph has been attached to this answer.

This graph has the intensity in dB on the y-axis and frequency on the x-axis. There are various curves plotted in the graph each corresponding to a specific intensity level at a defined standard frequency of 1000 Hz. So each plot on a curve denoted as 40 dB would sound as loud as that perceived from a sound with frequency of 1000 Hz and intensity of 40 dB.

To use the graph in order to answer the question, you simple look up the frequency, for example 60 Hz, on the x-axis and trace the line all the way up to the point it intersects with the curve labelled as "40 dB". From that point, go horizontally towards the y-axis to determine the intensity required for a sound at 60 Hz to sound as loud as the sound of 40 dB intensity at a frequency of 1000 Hz.

Answer 2

Answer:

For 60 Hz, = should be 60 dB

For 800 Hz, = should be approximately 38 dB

For 100 Hz, = should be 50 dB