How long for sound to reach us?

The answer depends on how fast do sound travel.

It is 347.3m/s at 27 Celsius at xx% humidity, near sea level.

Heheheh forgot the humidity levels J if someone remembers the textbooks value, please let me know J

For sound to travel 1m, it is 1/347.3 = 0.00287 seconds.

= 2.87 milliseconds


Q = Do sound reflects?

A = YES & NO, depends on what it hits.

Q = How do sound reflects?

A = Depends on the frequency wavelength and the angle of incident upon the object.

Q = How many reflections are they?

A = Unlimited, since sound is analogous.




  1. Introduction to Acoustics
  2. What are acoustics?
  3. How is sound created?
  4. What are the definitions of sound?
  5. How do sound travel?
  6. What is wavelength?
  7. Is sound a science?
  8. How do sound disperse?
  9. How long for sound to reach us?
  10. Do sound reflect?
  11. How do sound reflect?
  12. Do room volume affects sound?
  13. Do room shape affects sound?
  14. What is sound absorption?
  15. What is sound proof?
  16. How do sound wave summate or negate?
  17. Why do we need to know all these?



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Say for Home Hi-Fi: -

Listener generally seats 3 meters away from the speakers, therefore: -

So, for the sound to travel 3 m takes 3 / 347.3 = 8.6 ms

For the closest reflection = 1st reflection = 1st interference to original sound source = 4.1 m and it takes 4 / 347.3 = 11.5 ms

This means there is actually only 11.5 - 8.6 = 2.9 ms or PURE, real original sound

and hey, what happen to human's brain processing sound issue?

Human brains adopt around 35 ms of time window before processing it. This means in the 35 ms window, only 2.9 ms is pure, while 32.1 ms has invasion from reflections from all over the place, time and angle.

32.1 / 35 = 91.7 % are invasion by reflections :(

But wait, the music sound is continuous / non stop until it stops playing. Normal songs have an average time of 4 minutes, that's 4 x 60 x 1000 = 240,000 ms.

so, only the 1st 2.9 ms is considered the purest therefore 239,997.1 ms of invaded reflections time :(

so again 239,997.1 / 240,000 = 99.99879166666667% of the time humans are hearing sound in conjunction with reflections. Not pure.



For the case of Car Audio

Assuming right driver listening to right tweeter: -

direct sound path is around 0.5 m, assume reflection from ceiling, which has a traveling path around 0.7 m therefore

performing all the calculations as above..... it is also equivalent that 99.9999% of the time humans are hearing to sounds in conjunction with reflections. Not pure.