Intensity and Relative Amplitude

In summary, the intensity of a musical note is determined by its relative amplitude, which can vary between different instruments and create different timbres. The timbre of an instrument is defined by its spectral content, which can be influenced by the shape of its waveform and the presence of harmonics or overtones. However, calculating the harmonic content of a specific instrument, such as a violin, is a complex process due to the various elements that contribute to its unique sound.
  • #1
yahooid2
How would you calculate the intensity using relative amplitude.

Say for a violin...how would you calculate it's intensity for one of it's harmonics or overtones.
 
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  • #2
What dou you mean by "relative amplitude"?

I hope this doesn't turn into a Fourier discussion..

Jonathan
 
  • #3
like say in a wave...a musical note will create a similar frequency in different instruments, but the relative amplitude differs from instrument to instrument creating a different timbre or tone.
 
  • #4
The tonal qualties of differnt instrumnets come from the different shapes of their waveforms not from their amplitudes (the amplitude of a note is merely a measure of it's volume).
 
  • #5
To add to what jcsd said, the timbre of an instrument is defined by its "spectral content."

Think about this: a very boring instrument might play a single, pure sine wave of one frequency. The sound is bland and featureless, and won't impress most audiences.

Now add a little second harmonic -- in other words, if the basic note is middle C, add a little of the C one octave up. Be careful not to add too much -- the middle C should still be the loudest component. This new sound is a little more pleasing -- you can still tell it's a middle C, since the component with the largest amplitude is middle C -- but now the sound has a different timbre.

Real musical instruments have spectral content all over the place -- mostly in harmonics. The loudest note is called the fundamental, and notes of twice, three times, and four times that frequency are called the second, third, and fourth harmonics, and so on. Real instruments' sounds are defined by the amplitudes of all those harmonics -- they're often called "overtones" by musicians. That's why a saxophone and a piano sound very different, even when they both play middle C.

- Warren
 
  • #6
And to answer your question, I'm not sure there's really any way to calculate the harmonic content of a violin, for example -- it's a complicated system. The shape of the resonant cavity, the vents, the bridge, etc. all come into play. You might be able to get a first approximation by just analyzing the resonance of a simple cavity, but it won't capture all the complexity that makes a real violin sound so nice.

- Warren
 
  • #7
A pure sinusoid sounds cool, kind of eerie.

The fundamental does NOT have to be the loudest, just the lowest.

The spectrum of a piano is nonlinear (meaning Fourier analysis doesn't work well to describe the timbre).

The most important feature of a violin that causes the spectrum is the bow. The wave is predominantly sawtooth, and it doesn't require a terribly faithful reconstruction to simulate. The sawtooth is caused by the bow grabbing the string, pulling it, and then letting go sharply.
 
  • #8

1. What is intensity?

Intensity refers to the amount of energy per unit area that is carried by a wave. It is typically measured in watts per square meter (W/m^2). In terms of sound waves, intensity is related to the loudness of the sound.

2. How is intensity related to amplitude?

Intensity and amplitude are directly proportional to each other. This means that as the amplitude of a wave increases, the intensity also increases. This relationship can be described by the inverse square law, which states that intensity is inversely proportional to the square of the distance from the source.

3. What is relative amplitude?

Relative amplitude refers to the ratio of the amplitude of a wave to a reference amplitude. This reference amplitude can vary depending on the context, but it is usually a standard or baseline amplitude used for comparison.

4. How is relative amplitude different from absolute amplitude?

Relative amplitude takes into account the context of the measurement and is a comparison to a reference amplitude. Absolute amplitude, on the other hand, is a measure of the actual size or magnitude of the amplitude without any reference point. It is an absolute value and does not consider any external factors.

5. Can intensity and relative amplitude be used interchangeably?

No, intensity and relative amplitude are not interchangeable. While they are both related to the amplitude of a wave, they measure different aspects of it. Intensity is a measure of energy, while relative amplitude is a measure of comparison to a reference amplitude.

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