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I am doing a project in music where we have to make our own instrument and i have chosen to make a guitar. One of the questions we have to answer is; Explain how your instrument demonstrates the following sound qualities? The one that I'm stuck on is volume...

Can someone help me out??

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    I'm guessing that just means you have to show how it can play at different volumes? Which you do by plucking the strings softer or harder. – MattPutnam Apr 5 '16 at 1:15
  • Since you have tagged acoustic guitar, I'll assume that you are building an acoustic guitar. So the volume depends on how hard you strum. Also the sound hole plays a role in maintaining the volume as well. – Sahan De Silva Apr 5 '16 at 2:21
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Wow. If you are actually going to make a guitar then I must say that is quite challenging. I have a friend who is a woodworker who tried to make several guitars - but they just did not work out so well.

Here is what I can share about volume as it relates to guitars.

Let's start with an acoustic guitar (no electronics to amplify the sound). An acoustic guitar produces sound when a plucked (or otherwise excited) string vibrates the soundboard. Let's examine this in more intricate detail.

Plucking the string itself will not create much of an audible sound. So the string by itself does not produce the sound. Rather the string vibrates at a given frequency (depending on how it's tuned and fretted) which then vibrates the saddle (at that frequency) which sits atop the bridge which is attached to the top - also known as the soundboard. When the soundboard vibrates at the frequency transferred from the vibration of the string, audible sound is produced. To a lesser extent, the vibrations of the back and sides will also contribute to some sound. But the top itself is optimized to be the most sensitive to vibration induced by the strings.

Much of the sound created by the top and back and sides emanates through the sound hole, so the size of the soundhole can affect the volume as well (although you can plug the soundhole and still get a great deal of sound).

To a much lesser extent the vibrating string vibrates the nut which in turn vibrates the neck which can send some secondary vibration to the top which contributes to a sound sustaining.

The amount of volume a given acoustic guitar is capable of producing depends on many factors including the type and stiffness of the wood used, they type and design of the bracing, the shape of the guitar, the size of the guitar and the type and gauge of strings used. Other factors would even include the action or how high the strings sit above the fretboard.

On any given acoustic guitar, the volume is controlled by the velocity of the action used to set the string into motion. In other words the more forcefully you strike the string with a pick or pluck it with your finger or thumb - the more it will vibrate the top and the louder the sound will be. The thickness of a pick will affect the picks ability to excite the string (thicker picks will allow for more volume than thinner picks).

The volume can be attenuated by techniques such as palm muting or muting with the fretting hand. Either type muting can slow or stop the vibration and lower the volume.

An electric guitar depends on electronics and amplification to produce sound. The string vibration is detected by a magnetic pickup which sends an electrical signal to an amplifier which sends a signal to a speaker in the amplifier. When the speaker cone vibrates (at a frequency determined by the strings vibration) - audible sound is produced. The volume of sound on an electric guitar can be controlled similarly to an acoustic but is also controlled by volume knobs on the guitar itself as well as volume and gain controls on the amplifier.

I hope I have provided something you can use and for those not working on a music project - something of interest.

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    Excellent answer! Having made various guitars over the years, I'd suggest the OP go with an electric guitar. Acoustic guitars are incredibly difficult to make, as the entire body (shape, choice of wood, thickness of wood, sound holes etc) determines the sound, volume, tone and sustain, whereas an electric guitar can be successfully made from a plank of wood... – Doktor Mayhem Apr 5 '16 at 8:05
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    @DrMayhem I totally agree. I have another musician friend who regularly builds very nice and very playable electrics that look and sound just like the ones they are modeled after (Fender Strat, Gibson Les Paul, Gibson SG, etc.) He won't even attempt an acoustic for the reasons you mentioned. I have another friend who went to a renowned Luthier school for a year and it took multiple failures before he was able to master the art. Now he owns Hasty Custom Guitars and builds great sounding acoustics - but he's been at it for many years. Another friend tried acoustics but they all failed. – Rockin Cowboy Apr 5 '16 at 18:28
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Excellent explanation by Rockin Cowboy. On a purely pratical side I would add that volume is a sound property that can be easily measured, at least on relative terms. A number of free APPs for mobile phones are available that measure the sourrounding sound intensity. These are not professional tools, of course, but provide a good enough comparison of intensity for two different instruments, etc.

In my Android phone I use for example Sound Meter (from SMART TOOLS) and SPL Meter (from Keuwlsoft). They are (as many similar other) freeely available on the Google App Store.

Now, these tools measure physical pressure levels caused by sound (hence SPL=Sound Pressure Level :-). Strictly speaking this is not "volume", as "volume" (the perceived loudness) depends on additional factors like the frequencies involved and the average response of the human ear to such frequencies. However, for the purpose of the exercise, I suppose it would be a good enough approximation to demonstrate the sound quality of "volume" by measuring the resulting intensity from plucking a string in a reference frequency (say, A4=440Hz).

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