write the demonstration of loudness from demonstration?
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Answers
Explanation:
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Answer:
number of demonstrations were created to help instructors teach their students about the human auditory system and its limitations. In order to understand the demonstrations and the concepts behind them, some background material and detailed explanations are given for each topic.
Decibels
Decibels are defined as a logarithmic unit of sound intensity. Mathematically a decibel (dB) is defined as:
Where P1 and P2 are powers in Watts. Decibels can also be calculated using amplitudes. The above equation becomes:
Where A1 and A2 are amplitudes.
A logarithmic scale provides a relative measure of sound intensity. Based on powers of 10, decibel units allow a manageable range of numbers to represent the wide range of the human auditory response. The other reason a logarithmic scale is used when discussing sound is due to the fact that the human auditory system works loosely on a logarithmic scale. Our ears respond to ratios rather than differences, with the smallest perceptible change in loudness that the human auditory system can distinguish being roughly 1 dB.
Based on this information a series of three sound clips were developed to demonstrate decibel scales. This gives the student an opportunity to become familiar with incremental steps in hearing and to get familiar with the decibel concept that is used throughout the compact disc.
In the first demonstration, track 1, we hear a 440 Hz tone (A4 on the musical scale). The tone is then reduced in 1 dB steps. On tracks 2 and 3 the tone is reduced in steps of 3 dB and 5 dB respectively. Students will notice only minor changes in loudness in the first demonstration. The second and third tracks will allow them to hear more significant changes in loudness.
Intensity vs. Loudness
Sound intensity is a measurable quantity relating to acoustic energy whereas loudness is a subjective quality affected by the human auditory response to sound.
The Sonic Research Studio at Simon Fraser University defines sound intensity as “The sound energy transmitted per unit time through a unit area, thereby being a measure of the magnitude of a sound.” This ‘magnitude of sound’ is measured in Sound Pressure Levels (SPL) and is defined as:
Where Pref = 20 µPa = 10-12 W/m2. It is also known that the intensity of sound decreases according to the inverse square law, where r is the radius from the sound source.
So, how does sound intensity relate to perceived loudness? As mentioned above, loudness is subjective. What seems twice as loud to one person, may not be twice as loud to another. In the 1930s, two employees at Bell Labs, Harvey Fletcher and Wilden Munson, wanted to make a correlation between sound intensity and loudness. They asked a group of people to judge when pure tones of two different frequencies were the same loudness. They averaged their results and came up with a graph now known as Fletcher-Munson curves (Figure 1).
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