Final answer:
To determine the direct modification of loudness, you need to know the frequency and intensity level of the sound. You can use the graph and interpolate between loudness curves to find the loudness in phons. For a given frequency and loudness, you can find the corresponding intensity level in decibels.
Step-by-step explanation:
To determine the direct modification of loudness, you need to know the frequency and intensity level of the sound. From the given information, you have the frequency and intensity level for different sounds. For example, (a) You can use the graph in Figure 17.34 to locate the point for a 100-Hz sound at 80 dB and then interpolate between loudness curves to find the loudness in phons. (b) Similarly, you can find the intensity level in decibels of a 4000-Hz sound with a loudness of 70 phons by finding the point on the graph and reading the corresponding intensity level. (c) To find the intensity level at which an 8000-Hz sound has the same loudness as a 200-Hz sound at 60 dB, you need to find the intersection point of the curve for the 200-Hz sound and the curve for the 8000-Hz sound.