Doppler Effect: How Does the Ambulance Siren Vary?

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SUMMARY

The discussion centers on the Doppler Effect, specifically how the frequency of an ambulance siren changes as it approaches and passes a stationary observer. When the ambulance moves towards the observer at a constant speed, the observed frequency remains steady until it passes, at which point it decreases. The equation used for calculating the observed frequency is f = f1 x c / (c - V), where f1 is the source frequency, c is the speed of sound, and V is the source velocity. The conversation also touches on scenarios involving accelerating sound sources, such as kamikaze planes, and clarifies that the Doppler Effect applies to both constant and variable velocities.

PREREQUISITES
  • Understanding of the Doppler Effect and its implications in sound waves.
  • Familiarity with basic physics equations, particularly those involving frequency and velocity.
  • Knowledge of sound wave properties, including frequency and pitch.
  • Ability to perform calculations involving speed of sound and relative motion.
NEXT STEPS
  • Study the mathematical derivation of the Doppler Effect equations for sound waves.
  • Learn about the effects of acceleration on the Doppler Shift in various contexts.
  • Explore real-world applications of the Doppler Effect in fields such as astronomy and radar technology.
  • Investigate how the Doppler Effect is perceived in different mediums, such as water or air.
USEFUL FOR

Physics students, audio engineers, sound designers, and anyone interested in the principles of wave motion and frequency modulation.

  • #31
Turv said:
Gentlemen,

You don't just need to accelerate to achieve the doppler effect, it works with constant velocity too.

My formula is correct .
So are you saying, after all this nonsense, that you are really just talking about sound sources with constant velocity? No acceleration?

Rather than waste everyone's time with vague statements, if you have a question or statement about applying the Doppler effect, please state it clearly and completely.
 
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  • #32
Doc,

No disrespect to you but i think i have been clear, i stated the equations in constant velocity, its blatantly obviously it will still work with acceleration, I've never been the one confused.

And to be honest i think you mentors have been harsh and trying to ridicule me, i thought these forums were all about debate? learning from each other? not trying to pick fault of the slightest pathetic alleged miss used word.

What have i got to do go yes mentor you right every time you disagree with me? if I'm wrong I'm wrong but put calculations up.

Just remember " Ridicule may be a shield, but its not a weapon".
 
  • #33
Turv said:
Doc,

No disrespect to you but i think i have been clear, i stated the equations in constant velocity, its blatantly obviously it will still work with acceleration, I've never been the one confused.
Note that it was you, in post #4, who said you were confused. (Note that the OP's example involved an ambulance moving at constant speed.)
 
  • #34
ok, seeing as this came up on the f1 thread and was then rightly deleted.

Turv, you're wrong mate. If a constant speed (anything) heads DIRECTLY towards you you won't hear a pitch change. If it comes PAST to you, you will.

Even the shoddyness that is wiki has this on it.
 
  • #35
Chris,

I have just had a warning off a mentor which is totally unjustified, the doppler equation will work with constant velocity are you saying everything needs to accelerate to get the doppler effect, this would just be nonsense, if the mentors want (yes men) then why not ban everyone and have morons posting saying yes mentor 3 bags full mentor, yes your right mentor ( When they can't even post the equation in there defence) i posted the authentic doppler equation, is he wrong? YES MENTOR!
 
  • #36
http://www.school-for-champions.com/science/sound_doppler_equations.htm

Read 'Source Moving at an Angle' section.
 
  • #37
xxChrisxx said:
Turv, you're wrong mate. If a constant speed (anything) heads DIRECTLY towards you you won't hear a pitch change. If it comes PAST to you, you will.
You are correct, of course. Part of the problem here is sloppy language. When something comes directly toward you at constant speed, you will hear an unchanging, constant pitch which will be higher than the pitch of the source (and as given by the usual Doppler equations). If it goes past you, then you'll hear a changing pitch.

Turv said:
Chris,

I have just had a warning off a mentor which is totally unjustified, the doppler equation will work with constant velocity are you saying everything needs to accelerate to get the doppler effect, this would just be nonsense, if the mentors want (yes men) then why not ban everyone and have morons posting saying yes mentor 3 bags full mentor, yes your right mentor ( When they can't even post the equation in there defence) i posted the authentic doppler equation, is he wrong? YES MENTOR!
:rolleyes: Haven't you embarrassed yourself enough?
 
  • #38
Turv said:
xxChrisxx said:
ok, seeing as this came up on the f1 thread and was then rightly deleted.

Turv, you're wrong mate. If a constant speed (anything) heads DIRECTLY towards you you won't hear a pitch change. If it comes PAST to you, you will.

Even the shoddyness that is wiki has this on it.
Chris,

I have just had a warning off a mentor which is totally unjustified, the doppler equation will work with constant velocity are you saying everything needs to accelerate to get the doppler effect, this would just be nonsense, if the mentors want (yes men) then why not ban everyone and have morons posting saying yes mentor 3 bags full mentor, yes your right mentor ( When they can't even post the equation in there defence) i posted the authentic doppler equation, is he wrong? YES MENTOR!
Hold on! Don't get too excited!

When we talk of change, change relative to what?

When a car heads straight towards you, its frequency will have changed relative to what it would have been if it was stationary. But if you've never heard it stationary, you won't know that, you'll just hear a constant higher pitch. (If you did hear it when it was stationary, then you'd hear the pitch increase as it accelerated.) Then the car will hit you and you won't hear anything at all, because you'll be dead.
 

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