How far can sound travel?
Discussion
As per the title. I heard an airliner in the climb the other night. I live in a city so it is never quiet. Checked the plane on an App I have and it was about 20 miles from me. This was a modern quiet ish airliner, not a noisy warplane.
A few years ago, I heard a firework display at my home. I knew where it was taking place, 9 miles away as the crow flies.
I know there are dozens of variables, wind direction etc.
Apparently in Kent, you could ear the guns of flanders.
A few years ago, I heard a firework display at my home. I knew where it was taking place, 9 miles away as the crow flies.
I know there are dozens of variables, wind direction etc.
Apparently in Kent, you could ear the guns of flanders.
reggie82 said:
davepoth said:
Assuming there's things to vibrate, sound travels pretty much forever. Whether you can hear it is a different matter.
Wont it slowly turn into heat energy and fade out completely?Genuine question, not saying you're wrong
Dr Doofenshmirtz said:
It's like dropping a stone into a lake - the resulting ripples eventually die down. Sound doesn't travel forever.
The energy (the sound) is dissipated as it spreads (as Doofenshmirtz says) to the point where it becomes indistinguishable from other energies (wind /other sounds) and /or so low powered it can not move the ear drum.MX7 said:
They heard the Buncefield fire in Holland.
I'm convinced I did too and I'm in Edinburgh. I was still up after a night out, surfing the net and I heard a faint whistling noise. I say faint, but still loud enough to make me think what the hell was that and getting up to have a look out of the window. Obviously nothing to see and didn't think any more of it until I saw the news later on that day. I was never sure as I didnt know if it was possible to hear something from 350-400 miles away, but if it was heard in Holland ...Jimmy Two Times said:
MX7 said:
They heard the Buncefield fire in Holland.
I'm convinced I did too and I'm in Edinburgh. I was still up after a night out, surfing the net and I heard a faint whistling noise. I say faint, but still loud enough to make me think what the hell was that and getting up to have a look out of the window. Obviously nothing to see and didn't think any more of it until I saw the news later on that day. I was never sure as I didnt know if it was possible to hear something from 350-400 miles away, but if it was heard in Holland ...
Moving to the electromagnetic spectrum, it's like me as a schoolboy wondering by how much, if you struck a match on Earth, the temperature would go up on Pluto. I concluded it came down to quanta, and eventually 1's become 0's. Whether sound is the same I don't know - is it analogue or digital?
jurbie said:
Possibly you did however Holland maybe abroad but it is still damn sight closer to Buncefield (about 240miles to Amsterdam as the crow flies) than Edinburgh (310 miles). In fact at it's closest point Holland is about 170 miles away. [/geek]
Conversely I was in Hertford and didn't hear a bloody thing!I heard a dit which I believe to be genuine, that in the 80's one of our RN ships sonar sets in the English Channel detected and identified QE2 leaving New York Harbour. There were some very favourable sonar conditions bouncing the sound wave between the surface and the temparture layer for the whole distance.
Simpo Two said:
Moving to the electromagnetic spectrum, it's like me as a schoolboy wondering by how much, if you struck a match on Earth, the temperature would go up on Pluto. I concluded it came down to quanta, and eventually 1's become 0's. Whether sound is the same I don't know - is it analogue or digital?
The universe isn't digital you know. We don't really live in The Matrix. Sure, a signal can get lost down in the thermal noise, but there are ways around this. Bandwidth reduction, supercooling, multiple long baseline synthetic aperture receivers etc.http://en.wikipedia.org/wiki/Noise_floor
Amazingly, it is measurable. Sort of. When sending out space probes, engineers have to do something called a link budget calculation. This takes things like distance, transmit power, transmit frequency, bandwidth, antenna gain and receiver gain, and come up with a number.
I'm sure you know that light and radio are just different forms of electromagnetic waves, and can be treated similarly. If the signal dropped off too quickly, we simply wouldn't be able to communicate with the space probes. Think of it this way. If you sat on Pluto and pointed a modest 1kW laser beam at the earth, could you detect it with something like the Hubble space telescope? I reckon you could.
Have a play here http://www.microwave.gr/content/jsffield.htm
Well the point behind my use of 'analogue' and 'digital' was:
Analogue - attenuates, probably in a negatively logarithmical way, so that the line never quite touches the X-axis and there is always something to detect, even if infinitessimally small.
Digital - eventually 1 turns into 0 and that's it - nothing.
Electromagnetic radiation is, as I understand it, quantised, hence the thought that eventually it will attenuate to 0; ie nothing to detect. As for sound, I don't know.
Analogue - attenuates, probably in a negatively logarithmical way, so that the line never quite touches the X-axis and there is always something to detect, even if infinitessimally small.
Digital - eventually 1 turns into 0 and that's it - nothing.
Electromagnetic radiation is, as I understand it, quantised, hence the thought that eventually it will attenuate to 0; ie nothing to detect. As for sound, I don't know.
The ear is most sensitive around 1 kHz.
The dynamic range of the ear is around 140 dB.
The attenuation of sound in air at 1 kHz is around 5 dB/km.
Which gives around 28 km.
But if the source is much louder than the maximum level an ear can tolerate without damage - ie explosion, thunder etc then the distance would be increased.
The dynamic range of the ear is around 140 dB.
The attenuation of sound in air at 1 kHz is around 5 dB/km.
Which gives around 28 km.
But if the source is much louder than the maximum level an ear can tolerate without damage - ie explosion, thunder etc then the distance would be increased.
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