Question

a.How fast is sound? Does it seem to be instantaneous? Refer to your own experience as
a basis for your answer.
b. What units are the speed of sound measured in?
c. Write an equation of the speed of sound in terms of frequency and wavelength:
d. Look up the accepted speed of sound (m/s) at room temperature and record it here:
e. What is resonance? Give an explanation of the phenomenon. Why does the amplitude
of a sound wave go up when it resonates in a vessel?
f. What is an echo? When you hear an echo, is there a delay between making a sound and
hearing the echo? Why do you think that is?

Answer 1

a) How fast is sound :-

  Unfortunately, the answer is really not quite that simple.The speed of sound not a constant value. It varies by a small amount (a few percent) from place to place, season to season, morning to evening, and with water depth.The speed of sound is a term used to describe the speed of sound waves passing through an elastic medium.The speed varies with the medium employed (for example, sound waves move faster through water than through air), as well as with the properties of the medium, especially temperature Sound usually travels more slowly with greater altitude, due to reduced temperature.At sea level, at a temperature of 21 degrees Celsius (70 degrees Fahrenheit) and under normal atmospheric conditions, the speed of sound is 340 m/s (1238 km/h or 770 mph).

Sound can travel in air at approximately 340 metres per second. This is fast but not nearly as fast as light which travels at 300 000 kilometres per second. This difference in speeds enables us to appreciate that sound does take time to travel. When we see lightning the sound it produces at exactly the same time is often heard as thunder a few seconds later by an observer a few miles away. Unfortunately children will not always accept that the light and sound are from the same instantaneous release of energy. It is, however, possible to watch a sound being made at some distance away and to detect a slight delay in hearing the sound. Exploding fireworks, the click of a ball on a cricket bat and a child bashing a dustbin lid at the other end of a playing field will all provide this opportunity.

b. What units are the speed of sound measured in? :-

The SI unit for the speed of sound is metre per second i.e. m/s

can be measured in km/h or in mph or ft/s

speed of sound in air is about 343 metres per second (1,235 km/h; 1,125 ft/s; 767 mph; 667 kn), or a kilometre in 2.9 s or a mile in 4.7 s

c. Equation of the speed of sound in terms of frequency and wavelength :

The relationship of the speed of sound, its frequency, and wavelength is the same as for all waves: _Vw = fλ, where V_w is the speed of sound, f is its frequency, and λ is its wavelength.

d. Look up the accepted speed of sound (m/s) at room temperature and record it here:

The speed of sound in room temperature air is 346 meters per second. This is faster than 331 meters per second, which is the speed of sound in air at freezing temperatures.

e. What is resonance? Give an explanation of the phenomenon. Why does the amplitude
of a sound wave go up when it resonates in a vessel?

The definition of Resonance in physics is a phenomenon in which an external force or a vibrating system forces another system around it to vibrate with greater amplitude at a specified frequency of operation. The frequency at which the second body starts oscillating or vibrating at higher amplitude is called the resonant frequency of the body. The best examples of resonance can be observed in various musical instruments around us.

Whenever any person hits, strikes, strums, drums or tweaks any musical instrument, the instrument is set into oscillation or vibration at the natural frequency of vibration of the instrument. A unique standing wave pattern defines each frequency of vibration as a specific instrument. These natural frequencies of a musical instrument are known widely as the harmonics of the specified instrument. If a second interconnected object or instrument vibrates or oscillates at that specified frequency then the first object can be forced to vibrate at a frequency higher than its natural harmonic frequency. This phenomenon is known as resonance i.e. one object vibrating or oscillating at the natural frequency of another object forces the other object to vibrate at a frequency higher than its natural frequency.

When an external source plays a frequency that matches one of the harmonic standing waves of an object, a resonance can occur within the object. Resonance involves the reinforcement of a wave due to synchronized reflection of the wave. These “perfect reflections” can be induced by manipulating the neighboring environment, and are often used in medicine, such as in Magnetic Resonance Imaging (MRI). Resonance is exemplified by a large amount of energy transfer to the object and a dramatic increase in amplitude.

f. What is an echo? When you hear an echo, is there a delay between making a sound....

Sometimes when sound waves bounce off of a hard surface, you will hear the sound repeated again. For example, you might say ''Hello,'' and then a few seconds later, you hear the word ''Hello'' again. This called an echo. The sound waves left your mouth, traveled through the air, hit a hard surface, such as a wall, and then bounced back again, causing you to hear the sound again.

An echo is made by sound waves bouncing off a hard surface.
Have you ever wondered why you don't hear echoes for every sound that is made? The sound waves are typically absorbed before they hit something hard that they can bounce off of. But sometimes there still isn't an echo, even if you're in a place where there are no soft things to absorb the sound waves. Let's see if we can figure out why that happens.

Remember that the distance travelled by the sound is doubled for echo. (The sound “go there and come back”) For instance, if a sound wave takes 10 seconds to travel to the bottom of the sea and back, the total distance travelled is 2d, where d is the depth of the sea.

Hence, the velocity of the sound for echoes can be calculated by:

v=Total distance travelled by sound / Time taken

v = 2d / t