## Sounds Of Music C

UTF-8 U+6211 U+662F
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### Re: Sounds Of Music C

Jacobi wrote:I'm not sure whether this is under the purview of this event, but here it is:

What is the interval between:
1. The 2nd and 6th tones of a major scale?
2. The 4th and 7th tones of a harmonic minor scale?
3. The 3rd and 5th tones of a simple minor scale?
4. The 1st and 8th tones of any scale?
Perfect fifth, augmented fourth, major third, perfect octave (although this is only true for scales that have seven notes every octave...)

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### Re: Sounds Of Music C

UTF-8 U+6211 U+662F wrote:
Jacobi wrote:I'm not sure whether this is under the purview of this event, but here it is:

What is the interval between:
1. The 2nd and 6th tones of a major scale?
2. The 4th and 7th tones of a harmonic minor scale?
3. The 3rd and 5th tones of a simple minor scale?
4. The 1st and 8th tones of any scale?
Perfect fifth, augmented fourth, major third, perfect octave (although this is only true for scales that have seven notes every octave...)
Looks good.

UTF-8 U+6211 U+662F
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### Re: Sounds Of Music C

Describe the difference between sine waves and square waves. Include the sound they make.

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### Re: Sounds Of Music C

UTF-8 U+6211 U+662F wrote:Describe the difference between sine waves and square waves. Include the sound they make.
Sine waves are sinusoidal and are considered to be the most fundamental building block of sound, only containing the fundamental frequency. The human ear can recognize them as clear because they are representations of a single frequency with no harmonics. In contrast, square waves produce a square-like shape on a sound graph, quickly rising to a particular level, remaining constant, then instantly dropping to another level before returning to its original level. They contain odd harmonics along with the fundamental frequency, resulting in a notably rich, raspy sound.
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### Re: Sounds Of Music C

Knyte_Xjn wrote:
UTF-8 U+6211 U+662F wrote:Describe the difference between sine waves and square waves. Include the sound they make.
Sine waves are sinusoidal and are considered to be the most fundamental building block of sound, only containing the fundamental frequency. The human ear can recognize them as clear because they are representations of a single frequency with no harmonics. In contrast, square waves produce a square-like shape on a sound graph, quickly rising to a particular level, remaining constant, then instantly dropping to another level before returning to its original level. They contain odd harmonics along with the fundamental frequency, resulting in a notably rich, raspy sound.
Ha, "sine waves are sinusoidal".

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### Re: Sounds Of Music C

Since no one has responded with another question:

How does the intonation of each of the Hornbostel-Sachs instrument types change as temperature changes? Why do they react this way?
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### Re: Sounds Of Music C

The volume of an auditorium is 12000m^3. Its reverberation time is 1.5 seconds. If the average absorption coefficient of interior surfaces is .4 Sabine/m^2. Find the area of interior surfaces.
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### Re: Sounds Of Music C

mjcox2000 wrote:How does the intonation of each of the Hornbostel-Sachs instrument types change as temperature changes? Why do they react this way?
This is a pretty interesting question. It was hard to find any conclusive answers online so most of this is just my own analysis and so some of it is probably wrong or not the correct reasoning.
[b]Aerophone:[/b] Pretty straightforward. Aerophones function by vibrating the air - the speed of sound increases roughly linearly with temperature increase in Celsius (0.6 m/s for every 1 degree increase). Since the wavelength of the sound stays constant, the frequency must increase along with the increase in speed (and consequently decrease if the speed decreases). Another way this increase can be demonstrated is by the standard frequency formula $f=nv/2L$ (or 4L for closed). Since the velocity increases as temperature increases, the frequency also increases. Something to note is that as temperature increases, the instruments themselves would also expand slightly thus changing the length of the body. This would thus change the frequency as well since length is in the denominator. I'm pretty sure that the increase in velocity would be significantly larger than the increase in length (for example a steel flute that is half a kilogram will increase only .000018 meters at a 5 degree increase compared to a 3 m/s increase in velocity) however and thus the frequency would still increase as temperature increases.
[b]Idiophone:[/b] Idiophones have a pretty interesting formula for calculating frequency. This equation has velocity in the numerator (like aerophones) and thus change linearly with temperature change.
[b]Chordophone:[/b] This one has me stuck a bit. For calculating frequency of strings, one is supposed to use the velocity of the string, which is given by $f=\sqrt \frac Tu/2L$. An increase in temperature would increase the length of the string, and thus the frequency would be expected to [i]decrease[/i] since the length in the denominator is not under a square root. I'm not sure if this explanation is completely valid for Chordophones but some places online state that string instruments will become lower in pitch at higher temperatures.
[b]Membranophones:[/b] Membraphones are very complex in their frequency calculations as many more variables are taken into account. Humidity can have a large impact on these instruments, but holding all other things constant, it appears that frequency increases as temperature increases (and vice versa). One explanation for this is that a Timpani functions by vibrating the air inside the timpani. As already mentioned, the velocity of sound increases as temperature increases and thus the frequency would increase.
terence.tan wrote:The volume of an auditorium is 12000m^3. Its reverberation time is 1.5 seconds. If the average absorption coefficient of interior surfaces is .4 Sabine/m^2. Find the area of interior surfaces.
$t_r=.16V/sA$
$t_r= 1.5$
$V=12000$
$s=.4$
Solving for $A$ results in $A=3200 m^2$.
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### Re: Sounds Of Music C

Describe how to determine a note being played by looking at a Fast Fourier Transform and what a FFT is.
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### Re: Sounds Of Music C

terence.tan wrote:Describe how to determine a note being played by looking at a Fast Fourier Transform and what a FFT is.
Not totally sure about this, but gave it a shot... The FFT is an algorithm that divides a signal into its frequency components; this could be used to determine the note being played by doing an FFT on the input signal and looking at which frequency has the tallest spike (this should be said note); if the other frequencies are double or half the frequency of the tallest one, they're the same note in different octaves (harmonics)
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