# Quick echolocation question!

1. Jul 4, 2006

### physicsgal

if a dolphin swims towards some fish, and emits a high pitched sound. will the echo from this sound be observed (by the dolphin) as an increased/decreased frequency?

my vote is increased

~Amy

2. Jul 4, 2006

### Kurdt

Staff Emeritus
Yes should be. Analagous to the doppler effect in police cars etc.

3. Jul 4, 2006

### physicsgal

thanks

here's another question:
Vobserved = 2 m/s
Vsound = 330 m/s
Fsound = 96 Hz
Fobserved = ?

i calculated 96.58Hz or 9.7 * 10^1 Hz ?

~Amy

4. Jul 4, 2006

### Kurdt

Staff Emeritus
Yeah looks ok to me. Although is vobserved supposed to be the speed the dolphin is travelling?

5. Jul 4, 2006

### physicsgal

thanks. no dolphin in the 2nd question. it's about a band marching away from a guy a the speed of 2 m/s.

~Amy

6. Jul 4, 2006

### physicsgal

another question:

Find the second resonant length of an air column that resonates with a sound of frequency 1 kHz at 15 degrees C.

a) the air column is closed at both ends

b) the air colomn is open at both ends.

c) the air column is open at one end and closed at the other end.

can someone give me the formulas for b and c?

for a i figured out the wavelength to be 0.34085 m and the speed of sound to be 340.85m/s.

so the resonant length ends up being 34 cm.

~Amy

7. Jul 4, 2006

### physicsgal

update: for b i got 34 cm (same calculation as in "a")

and for c i got 25.5 cm

~Amy

8. Jul 4, 2006

### nrqed

Sounds all correct to me!

Patrick