Is the Echo Frequency Increased When a Dolphin Approaches Fish?

[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

 

[Kurdt]

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

 

[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

 

[Kurdt]

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

 

[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

 

[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

 

[physicsgal]

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

and for c i got 25.5 cm

~Amy

 

[nrqed]

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

and for c i got 25.5 cm

~Amy

Sounds all correct to me!

Patrick