What Is Decibel (Db) and What Is Its Importance in Sound Transmission Measurement

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  • Topic: Data compression, Run-length encoding, Lossless data compression
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  • Published : June 6, 2011
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Friday25th feb lecture Task
Do research and send your work to the email:abisonj@yahoo.com Task 1
What is decibel (dB) and what is its importance in sound transmission measurement. The dB is a logarithmic unit used to describe a ratio. The decibel ( dB) is used to measure sound level, but it is also widely used in electronics, signals and communication Use examples to explain how it can be used in multimedia measurement.

Using measuring of Loudness, phons and sones it can be used to explain how decibel(dB) can be used in multimedia measurement

The phon is a unit that is related to dB by the psychophysically measured frequency response of the ear. At 1 kHz, readings in phons and dB are, by definition, the same. For all other frequencies, the phon scale is determined by the results of experiments in which volunteers were asked to adjust the loudness of a signal at a given frequency until they judged its loudness to equal that of a 1 kHz signal. To convert from dB to phons, you need a graph of such results. Such a graph depends on sound level: it becomes flatter at high sound levels. The filters used for dBA and dBC

The most widely used sound level filter is the A scale, which roughly corresponds to the inverse of the 40 dB (at 1 kHz) equal-loudness curve. Using this filter, the sound level meter is thus less sensitive to very high and very low frequencies. Measurements made on this scale are expressed as dBA.

Task 2

Why is data compression necessary for Multimedia activities? Compression is useful because it helps reduce the consumption of expensive resources, such as hard disk space or transmission bandwidth . The multimedia data i.e. Audio and Video and Images take up too large memory, disk space or bandwidth when they are uncompressed.

(b) Difference between lossless and lossy compression? Give broad types of multimedia data are most suited for each? (5mk) Lossless Compression
Lossless compression recreates a compressed file as...
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