What is the Velocity of an Object if Soundwaves Behind it are 3 Octaves Lower?

In summary, the conversation discusses finding the velocity of an object based on the frequency shift of soundwaves behind it. One participant suggests using equations relating speed and frequency, while the other mentions the relationship between frequencies in octaves. Ultimately, it is determined that the problem can be solved without using Doppler effect equations by understanding the mathematical relationship between frequencies in octaves.
  • #1
Anabell
2
0

Homework Statement


Given the speed of sound in an environment, c = 300 m/s. We have an object moving with a ceratin velocity. If we know that the soundwaves behind the object are lower by 3 octaves than in front of it, then what is the velocity of the object?

2. Attempt at solving it.
I arrived at the conclusion that if the wavelength of the soundwaves in front of the object is x, then behind it is eight times of that (eg. x*8), since octaves are on a logaritmic scale. I don't know where to go on from here.
 
Last edited:
Physics news on Phys.org
  • #2
Where are your equations relating speed to frequency.

You know that f1 = 8 f2, where f1 is the frequency in the front and f2 is the frequency behind.

Plug these into your equations relating speed to frequency, and you should be able to solve for the unknown rest frequency and velocity.
(Two equations and two unknowns.)
 
  • #3
Dr. Courtney said:
Where are your equations relating speed to frequency.

You know that f1 = 8 f2, where f1 is the frequency in the front and f2 is the frequency behind.

Plug these into your equations relating speed to frequency, and you should be able to solve for the unknown rest frequency and velocity.
(Two equations and two unknowns.)
I don't have those equations, could you please ellaborate? :)

Do you mean speed = wavelength * frequency?
 
Last edited:
  • #4
You must have Doppler effect equations relating speed and frequency shifts for sources moving toward and away.
 
  • #5
Anabell said:

Homework Statement


Given the speed of sound in an environment, c = 300 m/s. We have an object moving with a certain velocity. If we know that the soundwaves behind the object are lower by 3 octaves than in front of it, then what is the velocity of the object?

2. Attempt at solving it.
I arrived at the conclusion that if the wavelength of the soundwaves in front of the object is x, then behind it is eight times of that (eg. x*8), since octaves are on a logarithmic scale. I don't know where to go on from here.
I don't think you need to use Doppler effect equations solve this.

If frequency, fB, is one octave above frequency, fA, then how is fB related to fA mathematically?
 

FAQ: What is the Velocity of an Object if Soundwaves Behind it are 3 Octaves Lower?

What is the Doppler effect?

The Doppler effect is the change in frequency or wavelength of a wave in relation to an observer who is moving relative to the source of the wave. It is commonly experienced with sound waves, such as the change in pitch of a siren as it passes by.

How is the Doppler effect calculated?

The Doppler effect can be calculated using the formula: Δf/f = v/c, where Δf is the change in frequency, f is the original frequency, v is the velocity of the observer, and c is the speed of the wave.

What factors affect the magnitude of the Doppler effect?

The magnitude of the Doppler effect is affected by the relative velocity between the observer and the source, as well as the speed of the wave. Additionally, the angle of incidence and the wavelength of the wave can also impact the magnitude of the effect.

How does the Doppler effect apply to different types of waves?

The Doppler effect can be observed in all types of waves, including sound, light, and water waves. For sound waves, it affects the perceived pitch, while for light waves, it affects the perceived color. In water waves, it can cause a change in the direction of the wave.

What are some real-world applications of the Doppler effect?

The Doppler effect has various practical applications, such as in weather radar to track the movement of storms, in medical ultrasound to measure blood flow, and in astronomy to determine the speed and direction of celestial objects.

Similar threads

Infinite time for an object to get K=0 conservative Force
Replies
10
Views
1K
I Compton's Effective Velocity and de Broglie == numerology?
Replies
1
Views
1K
Question on Heat, Pressure, and Doppler's Effect
Replies
1
Views
2K
I How can I identify the appropriate spectral line for Doppler calculation?
Replies
6
Views
2K
I Energy conservation in Doppler (NOT cosmological) redshifts?
Replies
13
Views
2K
The doppler effect and EM waves
Replies
4
Views
6K
Relativity With velocity of objects moving in different fram
Replies
1
Views
1K
I Doppler like effect affecting observed time for a moving object
Replies
1
Views
1K
What is the Formula for Calculating Doppler Effect in a Moving Train Scenario?
Replies
1
Views
4K
Understanding the Doppler Effect in Space-time Curvature
Replies
14
Views
4K

Hot Threads

Recent Insights

Back
Top