Dear Children, we have already discussed about the sources of sound and frequency of vibrations in the previous article. This article focuses on the three major sources of sound in detail and the means of changing their frequency.  

 

Musical instruments that produce sound by vibrating membranes. 

 

Musical instruments like the drums, thabla, and etc. produce sound through the vibration of their membrane. The frequency of the sound that is produced through these instruments can be raised by stretching the membrane more. For example, the membrane of a thabla can be stretched or loosened by loosening its strap. Here, the sound produced in both the instances differ from each other .When we consider a hand tightened timpani, the head tightens as we tighten the tuning handle  and it will produce a higher pitch. On the contrary, when the tuning handle is loosened, the head will also loosen resulting in a lower pitch. The frequency of the sound changes as we do certain changes to the membrane. Thus, the frequency of sound increases as the membrane is stretched. 

 

 

Musical instruments that produce sound by vibrating air columns 

 

The flute, tambourine and saxophone can be cited as some examples of these instruments. The frequency of sound produced in these instruments changes according to the length of air column that is vibrated within them. For an instance, the sound produced by a flute also changes according to the length of the air column that is vibrated by blowing air. The air pores present on the flute can be opened and covered using one’s fingers so that various sounds can be produced.

 

Musical instruments that produce sound by vibrating strings or rods

 

When the production of sound in the case of instruments such as the violin, guitar, sitar and etc. is concerned, it occurs by the mere vibration of strings or rods present in them. Several means of changing the sound produced by these instruments exist. When we tune a guitar, we change the length and the tension of the strings / wires of a guitar. When thin, tight and short wires are used in the instruments with strings, it results in a higher pitch whereas when the wires are long, thick and loose, the pitch gets lower. Hence, the sound produced by these instruments depend on the means and speed of vibration of strings. This scenario in the case of the instruments with vibrating bars can be explained through an example. The xylophone consists of bars/plates that vibrate to produce sound. Both short and long plates/bars are found in a xylophone. When we tap on shorter plates, it will produce a high pitch whereas tapping on the longer plates will result in a lower pitch. In this instance too, the frequency can be changed by changing the length of plates. (The shortest plate/bar will have the highest frequency and vice versa).

 

 

 

 

 

 

 

 

by Mekhala Egodawele

Photo source : Internet