What is Reverberation?

When attending an assembly inside the school auditorium, you must have observed how different the voice of the orator appears from the original. Also, the sound produced by the musical instruments during a concert in a closed hall appears very different when compared to its original sound. Ever wondered why? The answer to this lies in the concept of reverberation of sound.

What is reverberation?
Reverberation is the phenomenon of persistence of sound after it has been stopped by multiple reflections from surfaces within a closed surface. A reverberation is perceived when the reflected sound wave reaches your ear in less than 0.1 second after the original sound wave. Since the original sound wave is still held in memory, there is no time delay between the perception of the reflected sound wave and the original sound wave.

The two sound waves tend to combine as one very prolonged sound wave These reflections build up with each reflection and decay gradually as they are absorbed by the surfaces of objects in the space enclosed. Sound is a type of energy made by vibrations. When any object vibrates, it causes movement in the air particles.

This motion occurs through a medium occurs as one particle of the medium interacts with its neighboring particle, transmitting the mechanical motion. This movement, called sound waves, keeps going until they run out of energy. If your ear is within range of the vibrations, you hear the sound.

Loudness refers to how loud or soft a sound seems to a listener. Sound travels through air at 1,120 feet (340 meters) per second. Thus, frequency is determined by speed / wavelength. The longer the wavelength, the lower the pitch. The ‘height’ of the wave is its amplitude. The amplitude determines how loud a sound will be.

Greater amplitude means the sound will be louder. As sound waves travel farther from their source, the more spread out their energy becomes. As distance from the sound source increases, the area covered by the sound waves increases. The same amount of energy is spread over a greater area, so the intensity and loudness of the sound is less. This explains why even loud sounds fade away as you move farther from the source.

At Pusat Sains Negara (PSN), there is a roof’s structure is designed for the sound to travel in multiple reflections (Reverberation) as shown in figure below. Thus, your voice can be heard louder than your voice produced. Sound intensity is a measure of the energy of a sound wave and is a quantitative term that refers to a specific physical measurement: the energy carried by a wave through an area per unit of time.

The intensity varies as the square of the wave’s amplitude. Thus, the greater the difference between the regions of compression and rarefaction of the sound wave, the higher is its intensity. intensity is closely related to the more subjective word loudness, which refers to how the sound is perceived by us. For example, a sound that seems loud and out of place in a quiet room may be almost unnoticeable when it’s heard on a busy street corner, even though it has the same intensity.

Sources:

  1. https://byjus.com/physics/reverberation/
  2. https://www.ck12.org/physics/Intensity-and-Loudness-of-Sound/lesson/Intensity-and-Loudness-of-Sound-MS-PS/
  3. http://www.physicsclassroom.com/mmedia/waves/er.cfm