S302, Kewley-Port 10/21/07

Homework 9
Resonance, Filters, Noise

1. Most of the filter graphs in Chapter 6 are symmetrical (mirror images on high and low frequency sides). Explain what properties of impedance could make a filter assymetrical.

2. There are two tones, f1=200 Hz, and f2=1000. Both have a 55 dB IL sound level. If they are input to the filter above, what are the output sound levels for these two tones?

3. White noise has its bandwidth reduced by f  = 100Hz and has a level = 90 dB SPL. What is the
LPS?

a. 80 dB SPL
b. 70 dB SPL
c. 110 dB SPL
d. -20 dB SPL

4. A one octave filter has fc = 1500 Hz and slopes of 10 dB/octave?  Calculate f . Draw the filter curve on a spectral diagram. Estimate what the attenuation of the filter is at 4500 Hz.

5. Explain why the octave-band level is constant for pink noise.

6. If a bandpass filter has a wide bandwidth, explain whether it resonants in natural vibration with high or low damping and why. What resistance is associated with this filter?

7. The uniform amplitude spectrum shown in Fig. 6-6 is applied to low-pass filter in Fig. 6-12 with the 10 dB/octave roll-off. Draw the output spectrum after it is filtered (i.e. a line spectrum "Output" as seen in Fig. 6-6).

8. What does it mean on p. 203 that bandpass filter may be the result of a high-pass and low-pass filtering?

9. Explain what a 1/3 octave filter is and give examples of the "preferred center frequencies" for filters from 500 to 1000 Hz.