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At the end of this post, you will get an insight on the way sound works while you’re listening to music and/or when you’re at a performance that includes sound and music.
We all know that the harder we strum the guitar, the louder it gets and the louder it gets, the further away it is heard. This is because of the intensity a piece of music is played at. In other words, intensity refers to the amount of energy that is transported past a given area of the medium e.g air.
Amplitude of a wave refers to the maximum of displacement of a particle on the medium (air) from its rest position.
Loudness, in general, an increase in intensity will cause a sensation of increased loudness. But loudness does not increase in direct proportion to intensity. A sound of 50 dB has ten times the intensity of a sound of 40dB but is only twice as loud. Loudness doubles with each increase of 10 dB in intensity.
Loudness is also affected by frequency because the human ear is more sensitive to some frequencies than to others. The threshold of hearing — the lowest sound intensity that will produce the sensation of hearing for most people — is about 0 dB in the 2,000 to 5,000 Hz frequency range. For frequencies below and above this range, sounds must have greater intensity to be heard. Thus, for example, a sound of 100 Hz is barely audible at 30 dB; a sound of 10,000 Hz is barely audible at 20 dB. At 120 to, 140 dB most people experience physical discomfort or actual pain, and this level of intensity is referred to as the threshold of pain.
Decibel (dB) is the unit used to measure the power or intensity of sound. On the decibel scale, the smallest audible sound (near total silence) is 0 dB. A sound ten times more powerful is 10 dB. A sound 100 times more powerful than near total silence is 20 dB. A sound 1,000 times more powerful than near total silence is 30 dB. Here are some common sounds and their decibel ratings:
Near total silence — 0 dB
A whisper — 15 dB
Normal conversation — 60 dB
A lawnmower — 90 dB
A car horn — 110 dB
A rock concert or a jet engine — 120 dB
A gunshot or firecracker — 140 dB
Acoustics is the science of sound and its effect on people.
Like any wave, a sound wave just doesn’t stop. It passes through a medium into another and another or encounters an obstacle in its path. Sound is constantly being reflected off an object or diffracted around one.
Reflection sound is constantly being reflected off different surfaces. A sound wave hitting a wall at 45 degrees will reflect off at 45 degrees, sometimes the reflection can cause an increase in amplitude, phase cancellation, etc. Most of the time the reflected sound isn’t noticed because two identical sounds that reach the human ear less than 1/15 of a second apart cannot be distinguished as separate sounds. When the reflected sound is heard separately, it is called an echo or reverberation.
Acousticians pay the a lot of attention to this phenomena when building auditoriums or concert halls. A heavy reverb could cause a lot of problems for the act. A concert hall needs to be designed correctly with the right materials to absorb sound waves. Rough walls are used to diffuse sounds, reflecting it in a variety of directions. This lets the audience perceive sounds from every part of the room. Smooth walls tend to direct sound in one way and the audience sitting beside walls would hear it loudest and the auditorium wouldn’t seem lively and full of sound.
Echoes are slightly different to reverberations. Echoes occur when a reflected sound wave reaches more than 0.1 seconds after the original sound wave was heard.
This would answer your questions on why concert halls are oddly shaped.
Diffraction ever noticed how we can hear someone without seeing them? That’s because sound waves tend to spread and bend around objects. The amount of diffraction depends on the wavelength or the size of the object. Lower pitched sounds tend to travel better than high-pitched sounds. This is because they have longer wavelengths.
I trust you now have a better understanding of the diverse perceptions of sound and its behaviour on our planet.
