Question

Please show all your work.

1. A source of sound is located in a room a distance “L” from a wall. The room temperature is 72°F. AN observer is located between the source and the wall at 103 cm from the wall. The observer can hear a loud sound at the 3^rd harmonic and the sound fades at the 4^th harmonic.
   • What is the velocity of sound in the room?
   • What is the frequency at which the observer can hear the loud sound?
   • What is the wavelength associated with the frequency in question b?
   • What is the frequency at which the sound fades?
   • What is the wavelength associated with the frequency in question d?
2. On the Planet Vulcan a male Nameloc is flying toward his mate at 25 cm/sec while singing at a frequency of 1200 Hz. If the stationary female hears a tone of 1500 Hz, what is the speed of sound on Planet Vulcan?
3. A source is emitting sound at a frequency of 640 Hz. The source is rotating in a circle with radius of 85 cm and angular velocity of 25 rad/sec. The temperature of the environment is 82°F.
   • What is the lowest frequency heard by a listener at rest?
   • What is the highest frequency heard by the listener?
4. A point source is emitting sound isotopically (evenly in every direction). If the distance from the source is 3 times the original distance:
   • By how many dBs is the sound level changed?
   • Is the sound level increased/decreased? Why?
5. A source of sound is moving toward a wall. It is moving at a speed of 0.034 times the speed of sound. It is emitting sound at a frequency of 35,000 Hz. The temperature of the environment is 78°F. If the sound wave is reflected from a wall:
   • What is the frequency detected at the wall?
   • What is the frequency detected by the point source (after reflection/echo)?
6. A fishing board is using Sonar to detect the presence of fish below it. The sonar set sends out a pulse of sound at frequency of 40 MHz. the sound reflects from a whale directly below the board and the echo is received at a frequency of 40.042 Mhz 80 msec later. In water, V_SD = 1482 m/sec.
   • How deep is the whale?
   • How fast is it moving?
   • IN what direction is the whale moving?
7. A stone is dropped into a well 54 m deep. The temperature of the environment is 75°F. How long will it take for the splash to be heard?
8. Earplugs protect the hearing when being subjected to high levels of sound such as operating machinery or attending a Rock Convert. If earplugs decreased the sound level of sound waves by 20 dB, what is the ratio of the final intensity of the waves to the initial intensity?
9. An observer is listening to a stereo. The observer and the speaker are 20 ft apart and are located on a line which is parallel to and 7.5 ft away from a solid wall. The temperature of the room is 75°F.
   • What is the lowest frequency which should be audible but is not heard? (audible range is 20-20,000 Hz)
   • What is the lowest frequency which can be heard?

Answer 1