Velocity of Sound

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Experiment 7: Velocity of Sound

Jaybee J. Balilea, Sharmaine O. Baysic, Maria Anjelette Patricia C. Belen, Dianne Grace D. Bolloso

Department of Biological Sciences
College of Science, University of Santo Tomas
Espana, Manila

Sound is a mechanical wave that is an oscillation of pressure transmitted through a solid, liquid, or gas, composed of frequencies within the range of hearing and of a level sufficiently strong to be heard. It is produced when something vibrates causing its the medium (water, air, etc.) around it to vibrate as well. In common everyday speech, speed of sound refers to the speed of sound waves in air. Sound travels faster in liquids and non-porous solids than it does in air. In this experiment, velocity of sound in solid, liquid and gas were determined.

The wavelength of a sinusoidal wave is the spatial period of the wave—the distance over which the wave's shape repeats. It is usually determined by considering the distance between consecutive corresponding points of the same phase, such as crests, troughs, or zero crossings, and is a characteristic of traveling waves and standing waves, as well as other spatial wave patterns. Wavelength is commonly designated by the Greek letter lambda. Frequency is the number of occurrences of a repeating event per unit time. It is also referred to as temporal frequency. The period is the duration of one cycle in a repeating event, so the period is the reciprocal of the frequency. The speed of sound is the distance travelled during a unit of time by a sound wave propagating through an elastic medium. In the experiment, the group should be able to achieve the following objectives: (1) To verify about the relationship of Frequency of sound and its wavelength, (2) to determine the speed of sound by means of resonating column, (3)and to determine the velocity of sound in a solid using a vibrating rod.

The speed of sound is dependent on the medium through which the waves of sound travel. Sound travels slower in air in comparison with its travel in liquids and solids. The speed of sound in an object depends also on elasticity of the object. In fact, sound travels four times faster in liquids than in solids and around fifteen times faster in steel than in air. The properties that have an affect on the speed of sound in air are pressure, density, and molecular mass of the medium. The lower the density that of a medium, the faster the speed of sound and the higher the compressibility is, the slower the sound travels. The speed of sound in air is approximately 331.5 m/s at 0 °C or around 1200 km per hour. The speed of sound through air is approximately 343 m/s at normal room temperature, which is at 20 °C. The speed of sound through air is 346 m/s at 25 °C. The speed of sound in air is approximately figured out by the formula.

speed of sound (m/s) = 331.5 + 0.60 T(°C)

Wavelength is defined as the distance occupied by one cycle of wave at any instant. As mentioned earlier, it's the distance occupied between two regular crests or troughs of a wave. Wavelength can be measured in many ranges, from few hundredths of an inch to meters. The wavelength formula, also called wavelength frequency formula, is given below,

λ = c/f

Lambda (λ) = wavelength in any unit of length (generally meter) v = velocity of light = (m/s)
f = frequency in Hz

Here, we need to understand the definition of frequency. Frequency is defined as the number of times a wave passes through a point per second. Frequency is measured in hertz (Hz). The frequency formula is given by,

f = I/T
T = time of wave period in one cycle (in seconds)
f = frequency in Hz

Activity 1:
A tuning fork was struck with a rubber mallet and place at the top of a glass tube. The water vessel was then lowered slowly until the loudest sound was heard. The point where the sound was heard was marked. The distance beween the point and the top...
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