Sound Wave Physics: X-Axis vs. Trough

In summary, sound is dependent on amplitude and is zero on the x-axis. When listening to sound, it is perceived by the brain rather than the ears or scientific instruments. Loudspeakers are designed to follow the voltage graph on an oscilloscope, but there may be slight deviations. The air pressure and velocity close to the speaker is zero at the midpoint of the speaker, but there may be a time delay further away due to the finite speed of sound. Therefore, the sound wave is never completely silent and can be heard even at the peak and trough.
  • #1
ZB08
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Hi, easy one but can't really get my head around it. The physics teacher today showed sound as Sine wave on an oscilloscope. If I was actually listening to this sound wave, where would it be silent, on the x-axis or at the trough? Please explain.
 
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  • #2
Sound is dependent on the amplitude, so it is zero on the axis.
 
  • #3
If you are listening to it, you are "hearing the sound" with your brain. Not with your ears, and certainly not with a scientific measuring instrument! For almost all the frequency range where you hear anything at all, the loudness you hear will be constant.

On the other hand it we are talking about measuring what happens to the air wth scientific instruments rather than "what you hear", loudspeakers are designed so the position of the moving cone follows the voltage graph that you see on the oscilloscpe. (But a real loudspeaker isn't perfect, and won't follow it exactly). The change in air pressure, close to the speaker, is zero when the cone is at its mid point. However the velocity of the air close to the speaker is zero when the speaker is at the max and min displacements.

But further away from the speaker, there is a "time delay" because the speed of sound is finite - about 340 m/s so the peaks and troughs of the pressure and velocity further away from the speaker "lag behind" the movement of the speaker by an amount that is proportional to the distance away.
 
  • #4
ZB08 said:
Hi, easy one but can't really get my head around it. The physics teacher today showed sound as Sine wave on an oscilloscope. If I was actually listening to this sound wave, where would it be silent, on the x-axis or at the trough? Please explain.

It wouldn't be silent anywhere. It would only be silent if there was no wave at all; just a flat line. At the x-axis the wave actually has the highest rate of change. The rate of change is zero at the peak and the trough but even then there would still be sound.
 
  • #5
Thanks everybody
 

Related to Sound Wave Physics: X-Axis vs. Trough

1. What is the difference between the x-axis and trough in sound wave physics?

The x-axis in sound wave physics represents time, while the trough represents the lowest point of a sound wave's amplitude. This means that the x-axis shows the progression of the sound wave over time, while the trough shows the point of maximum displacement from the equilibrium position.

2. How does the x-axis affect the perception of sound?

The x-axis plays a crucial role in determining the frequency and wavelength of a sound wave, which in turn affects how we perceive sound. A higher frequency, represented by a shorter wavelength on the x-axis, is perceived as a higher pitch, while a lower frequency, represented by a longer wavelength, is perceived as a lower pitch.

3. What is the relationship between the x-axis and the amplitude of a sound wave?

The amplitude of a sound wave is represented by the height of the wave on the y-axis. The x-axis, representing time, shows how the amplitude changes over time. This means that the x-axis and amplitude are closely related, as changes in amplitude can be observed and measured over time on the x-axis.

4. Can the x-axis be used to measure the loudness of a sound?

Yes, the x-axis can be used to measure the loudness of a sound through the measurement of the sound wave's amplitude. The higher the amplitude, the louder the sound will be perceived. However, the perception of loudness is also affected by other factors such as distance from the sound source and the sensitivity of the human ear.

5. How does the x-axis change for different types of sound waves?

The x-axis may vary for different types of sound waves depending on their frequency and wavelength. For example, a higher frequency sound wave will have a shorter wavelength and therefore a shorter x-axis, while a lower frequency sound wave will have a longer x-axis. Additionally, the shape of the sound wave can also affect the x-axis, with more complex waveforms having a more irregular x-axis.

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