Please read chapter 7 from Miller's book.
Problem Set:
- A sinusoidal plane wave at 40 Hz. has an SPL of 80 decibels.
- How far does the air move? (I.e., what is its RMS displacement?)
- What is the change in SPL (in dB) if the wave maintains this RMS displacement, but the frequency changes to 80 Hz?
- A rectangular vibrating surface one foot long is vibrating at 1000 Hz. Assuming the speed of sound is 1000 feet per second, at what angle off axis should the beam's amplitude drop to zero?
- How many dB less does a cardioid microphone pick up from an incoming sound 90 degrees (pi/2 radians) off-axis, compared to a signal coming in frontally (at the angle of highest gain)?
- Suppose a sound's SPL is 0 dB. What is the total power that you ear receives? (Assume that the opening is 1 square centimeter).
Work on your final projects! Remember, they're due next week!
