ENVS 1200 Lecture Notes - Lecture 20: Sound
13 May 2018
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ENVS 1200 Tutorial 20 Notes – Analog Sound
Introduction
• It is important to know that the electromagnetic waves used for radio transmission are
also analog.
• It is often necessary or desirable to be able to transform a digital signal into some
analog equivalent representation or vice versa.
• For example, analog sound is stored digitally in an MP3 player.
• To listen to the audio on the player requires that the bits of data be converted to analog
waveforms.
• Headphones reproduce the waveforms as sound.
• Conversely, to transmit computer data on an ordinary voice-grade phone line requires
that the computer data must be represented by an analog signal
• Since the phone line is designed to carry sound.
• A modem is used to perform the conversion.
• Actually, to be more accurate, the phone line carries analog electrical voltage signals
that represent the sound wave, which are converted back to actual sound at the
earpiece of the phone receiving the signal.
• Ideally, the transformation between digital and analog should be reversible.
• That is to say, if we transform a digital waveform into an analog representation and then
transform it back, the resulting digital waveform should be identical to the original.
• For digital waveforms, this is theoretically achievable.
• In practice, all systems, both digital and analog, are subject to noise, attenuation, and
distortion
• It is often necessary to provide compensation in the form of error correction.
• Nonetheless, under most conditions, it is possible to recover the original digital data
exactly.
• When analog data is converted into digital form
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