Doppler Effect: How Does the Ambulance Siren Vary?

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    Doppler Doppler effect
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Discussion Overview

The discussion revolves around the Doppler effect as it pertains to the sound of an ambulance siren and other scenarios involving sound sources moving towards a stationary observer. Participants explore how the frequency of sound changes with relative motion, particularly focusing on whether the observed frequency varies continuously or remains steady as the source approaches or recedes.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • Some participants assert that the Doppler effect causes the siren of an approaching ambulance to sound shriller, while others question whether this frequency change is gradual or steady.
  • One participant provides a mathematical example of the Doppler effect, calculating the frequency observed when a sound source moves towards a stationary observer.
  • There is a discussion about whether the frequency remains steady when the source is moving directly towards the observer at constant speed, with some agreeing that it does, while others suggest that the frequency may change if the source is accelerating.
  • Participants debate the implications of sound frequency changes in different scenarios, such as military aircraft approaching a ship, with some arguing that acceleration affects the pitch heard by observers.
  • Concerns are raised about the terminology used in examples, with a participant noting that certain terms may be considered offensive and should be avoided.
  • Some participants express confusion over the definitions of "steady" frequency and whether it implies a constant value or a gradual increase.
  • There is a mention of the limitations of the Doppler effect equations when the source approaches the speed of sound, highlighting the mathematical implications of such scenarios.

Areas of Agreement / Disagreement

Participants express a mix of agreement and disagreement regarding the nature of frequency changes due to the Doppler effect. While some agree on certain mathematical interpretations, others challenge the assumptions made about the scenarios discussed, particularly regarding acceleration and the implications for sound frequency.

Contextual Notes

Some assumptions about the scenarios, such as the constant speed of the ambulance or the trajectory of aircraft, remain unresolved. Additionally, the discussion includes varying interpretations of terminology related to frequency changes.

  • #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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