Is the speed of sound relative?

In summary, the speed of sound is relative to the density of the medium it is traveling in and is affected by temperature. The speed of sound is also relative to the motion of the observer, with the speed increasing if the observer is moving towards the source of the sound. The same effect can be seen in supersonic jets, where the engine noise can only be heard inside the aircraft due to the shockwaves created by the high speed. While supersonic speeds are common in air travel, no vehicle has yet achieved Mach 1 at ground level. However, rocket sleds and the Thrust SSC have successfully exceeded the speed of sound.
  • #1
confused????
12
0
drunken musings... if i was sat on the wing of a jet traveling at mach2 would i be able to hear the the noise of the engine behind me?
 
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  • #2
No. Sound speed is Mach 1.
 
  • #3
So yes, speeds are relative if there must exist a medium of propagation (aka everything besides light). Actually that's kind of a cool thought experiment, almost makes me want to strap myself to a supersonic jet.
 
  • #4
No, the sound can only travel at Mach 1 rellative to the speed of the air.

You don't have to sit on the wing. The same effect occurred in Concorde when it accelerated through Mach 1 and the engine noise disappeared in the passenger cabin, apart from a small amount of noise transmitted through the structure of the plane itself and not through the air.

At a more "down to earth" level, this is the cause of the Doppler effect.
 
  • #5
It depends on what the speed of the flow is where your head is. Moving at supersonic speeds, shockwaves develop and slow the flow down. Behind the shocks, air is subsonic normal to the shock but may be supersonic overall. If it is subsonic everywhere, you could hear the engines. If it is supersonic, you couldn't. In all likelihood you wouldn't hear the engines.
 
  • #6
AlephZero said:
You don't have to sit on the wing. The same effect occurred in Concorde when it accelerated through Mach 1 and the engine noise disappeared in the passenger cabin, apart from a small amount of noise transmitted through the structure of the plane itself and not through the air.

Certainly not as cool of an experience, however.
 
  • #7
The speed of sound is relative to the density of the medium it is traveling in. Thus it is faster in water than in air and faster at ground level than at altitude. Although Mach 2 airflight is commonplace nowadays, no vehicle has achieved Mach 1 at ground level yet. The new land speed record attempt at 1000 miles an hour will seek to achieve that.

PS Global warming isn't a theory; it's a lie!
 
  • #8
Percussim said:
The speed of sound is relative to the density of the medium it is traveling in. Thus it is faster in water than in air and faster at ground level than at altitude. Although Mach 2 airflight is commonplace nowadays, no vehicle has achieved Mach 1 at ground level yet. The new land speed record attempt at 1000 miles an hour will seek to achieve that.

PS Global warming isn't a theory; it's a lie!

thats not what the OP asked. youre explaining why the speed of sound is related to density.

PS banned topic of discussion
 
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  • #9
Please explain difference - speed of sound depends on density of transmitting medium
 
  • #10
Percussim said:
Please explain difference - speed of sound depends on density of transmitting medium

speed of sound depends on the density means its related to the density.

the OP asked if the speed of sound was relative ie relative to the motion of the observer
 
  • #11
If the belief that global warming is a lie is banned, it proves that you have no support for its existence - QED
 
  • #12
Percussim said:
If the belief that global warming is a lie is banned, it proves that you have no support for its existence - QED

not at all, the argument itself is banned. you would be told off if you posted a tonne of scientific journals supporting global warming. also opinions can't be proven and QED is a pretty ridiculous thing to say there.
 
  • #13
Percussim said:
Speed of sound is not relative to the motion of the observer - heard sound is only only relative to your ear - ears do not observe. Would we hear a sound behind us - no - consider the Doppler Effect

what are you talking about?

if you move towards a source of sound at speed v, the speed of the sound waves relative to you is (340+v)m/s
contrast this with light where if you move towards a torch with velocity v, the speed of the light waves relative to you is c m/s, the speed of light.

Percussim said:
OK, I am banned - global warming is an opinion, so ban yourself - this is not a scientific site
the reason global warming is a banned topic is because this IS a scientific site and there is so much opinion and emotion involved whilst so little actual science is provided when people talk about it. moderating the discussion to ensure that it stayed scientific would require an expert (which this forum doesn't have) in the field to devote their time to moderating crackpot loony theories. because we don't have an expert here, the topic is banned in order to make sure that this site doesn't become a pseudo-science mess.
 
  • #14
Percussim said:
The speed of sound is relative to the density of the medium it is traveling in.
The speed of sound is related to the rate of propagation of a wave in the media, and it's also affected by temperature (speed of sound increases if temperature increases and vice versa).

Speed of sound is relative to the air, so if the air is moving, then the speed of sound is relative to the air. As far a a supersonic jet goes, much of the engine noise heard inside is traveling through the body of the aircraft, not through the air.

No vehicle has achieved Mach 1 at ground level yet.
Rocket sleds routinely achieve high mach speeds. The Thrust SST was the first "official" human driven vehicle to exceed the speed of sound.

Rocket sled going 6453 mph:


Thrust SSC (sonic boom at 2:30 into video):


A bit after 1:00 in this video, you can see the shock wave impact on the ground of the approaching Thrust SSC:


Enhanced photo of the Thrust SSC shock wave in attached image:
 

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1. What does it mean for the speed of sound to be relative?

The speed of sound being relative means that its value is not constant and can vary depending on certain factors, such as temperature and medium.

2. Is the speed of sound relative to the observer?

Yes, the speed of sound can be relative to the observer. For example, if a person is moving towards a sound source, they will perceive the sound to be faster compared to someone who is moving away from the source.

3. How does temperature affect the speed of sound?

Temperature plays a significant role in the speed of sound. As temperature increases, the molecules in a medium vibrate more, causing sound waves to travel faster. On the other hand, as temperature decreases, the molecules vibrate less, resulting in a slower speed of sound.

4. Does the medium affect the speed of sound?

Yes, the medium through which sound waves travel can affect their speed. For example, sound travels faster in solids compared to liquids and even slower in gases. This is because the molecules in a solid are closer together, allowing sound waves to travel more quickly.

5. Can the speed of sound be faster than the speed of light?

No, the speed of sound cannot be faster than the speed of light. The speed of light is the fastest speed at which any form of energy can travel, and sound waves do not have enough energy to surpass it. In fact, sound waves travel at a much slower speed compared to light waves.

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