What is a decibel scale ? Explain it by giving suitable examples How is hearing loss caused ?
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To define a decibel, we break it down into two parts. The first part, 'deci-,' is a metric prefix that denotes a factor of one-tenth. Therefore, a decibel is one-tenth of a bel. The second part, '-bel,' is a unit of sound intensity that represents the ratio of sound pressure level. The unit is named after Alexander Graham Bell. The threshold of hearing is zero bel (10^-12 watts per square meter). Sound intensity is often measured in decibels and rarely in bels. The decibel unit is denoted by the abbreviation dB and is often referred to by people using it as 'dee-bees.'
The decibel has also found widespread use in electrical and electronics engineering to describe ratios of power, amplitude, voltage, temperature, frequency, and data rate. Although the dB is referred to as a unit, it is really a dimensionless quantity. Stated another way, it is a ratio of two quantities, rather than a unit. Mathematically, the units of the two quantities divide out, leaving it dimensionless. In these cases, the quantity is usually expressed as dB relative to another quantity. This is shown later in the lesson in several examples.
To give you some examples of how dB applies to sound, the sound levels to which we are routinely exposed to in everyday life range from zero dB to 120 dB. Sound levels over 85 dB are dangerous to hearing and levels above 120 dB can cause ear pain and permanent hearing loss. The graphic below shows the dB scale with some representative examples of sounds at each level.
The decibel has also found widespread use in electrical and electronics engineering to describe ratios of power, amplitude, voltage, temperature, frequency, and data rate. Although the dB is referred to as a unit, it is really a dimensionless quantity. Stated another way, it is a ratio of two quantities, rather than a unit. Mathematically, the units of the two quantities divide out, leaving it dimensionless. In these cases, the quantity is usually expressed as dB relative to another quantity. This is shown later in the lesson in several examples.
To give you some examples of how dB applies to sound, the sound levels to which we are routinely exposed to in everyday life range from zero dB to 120 dB. Sound levels over 85 dB are dangerous to hearing and levels above 120 dB can cause ear pain and permanent hearing loss. The graphic below shows the dB scale with some representative examples of sounds at each level.
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Explanation:
A logarithmic scale with a base ten used to measure sound level is called a decibel scale. On the decibel scale, the smallest audible sound (close to overall silence) is 0 dB. A sound ten times more effective is 10 dB. A sound one hundred time more effective than close to overall silence is 20 dB. A sound 1000 times more effective than close to overall silence is 30 dB. Any sound above 85 dB can lead to a loss in listening, and the loss is associated with the power of the sound in addition to the period of exposure.
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