2120 pho 10 phon 100 phors 120 100 90 phon 80 phon 70 phon 60 phon 50 phor 40 phon 30 phon 60 40 20 phom 10 phon 20 -0 phon -10 40 60 100 200 400 800 50 80 5000 10,000 8000 4000 2000 500 1000 Frequency f (Hz) Figure 17.36 The relationship of loudness in phons to intensity level (in decibels) and intensity (in watts per meter squared) for persons with normal hearing. The curved lines are equal-loudness curves-all sounds on a given curve are perceived as equally loud. Phons and decibels are defined to be the same at 1000 Hz. Sound level (dB)
Properties of sound
A sound wave is a mechanical wave (or mechanical vibration) that transit through media such as gas (air), liquid (water), and solid (wood).
Quality Of Sound
A sound or a sound wave is defined as the energy produced due to the vibrations of particles in a medium. When any medium produces a disturbance or vibrations, it causes a movement in the air particles which produces sound waves. Molecules in the air vibrate about a certain average position and create compressions and rarefactions. This is called pitch which is defined as the frequency of sound. The frequency is defined as the number of oscillations in pressure per second.
Categories of Sound Wave
People perceive sound in different ways, like a medico student takes sound as vibration produced by objects reaching the human eardrum. A physicist perceives sound as vibration produced by an object, which produces disturbances in nearby air molecules that travel further. Both of them describe it as vibration generated by an object, the difference is one talks about how it is received and other deals with how it travels and propagates across various mediums.
(a) What is the loudness in phons of a 100-Hz sound that has an intensity level of 80 dB?
(b) What is the intensity level in decibels of a 4000-Hz sound having a loudness of 70 phons? (c) At what intensity level will an 8000-Hz sound have the same loudness as a 200-Hz sound at 60 dB?
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