What is digital audio?
Digital audio is a representation of sound recorded in, or converted into, digital form, where the sound wave is encoded as numerical samples in a continuous sequence.
In CD audio, how often are samples taken?
Samples are taken 44,100 times per second (44.1 kHz).
What is the bit resolution of CD audio?
CD audio has 16-bit resolution for each stereo channel.
What does ADC stand for and what does it do?
ADC stands for analog-to-digital converter. It converts an analog electrical signal into a digital signal.
What does DAC stand for and what does it do?
DAC stands for digital-to-analog converter. It converts a digital signal back into an analog signal for playback.
What is pulse-code modulation (PCM)?
PCM is a method used to convert an analog signal to a digital signal by sampling the amplitude at regular intervals.
What is the sampling rate?
The sampling rate is the number of samples taken per second, measured in hertz (Hz).
What is bit depth (resolution)?
Bit depth is the number of bits used to represent each sample, determining the precision of the amplitude measurement.
How does increasing the sample rate affect quality and file size?
Increasing the sample rate improves the accuracy of the recorded frequencies (higher frequencies can be captured) but also increases file size.
How does increasing the bit depth affect quality and file size?
Increasing bit depth improves the dynamic range and reduces quantization error, but also increases file size.
What is the Nyquist frequency?
The Nyquist frequency is half the sampling rate. Frequencies above this cannot be accurately represented and can cause aliasing.
What is an anti-aliasing filter?
An anti-aliasing filter is used before conversion to remove frequencies higher than the Nyquist frequency to prevent aliasing distortion.
What is aliasing?
Aliasing is distortion caused when frequencies above the Nyquist frequency are incorrectly represented as lower frequencies during sampling.
How does playback reconstruct the original sound wave?
A DAC converts the digital samples back into an analog signal, and according to the Nyquist–Shannon sampling theorem, the original band-limited signal can be accurately reconstructed.
What is the advantage of digital audio over analog audio in terms of copying?
Digital audio allows an infinite number of copies to be made without any degradation of signal quality, unlike analog which suffers generation loss.
What is channel coding?
Channel coding is a technique used to encode a digital signal for error correction during storage or transmission, maintaining bit accuracy.
What is eight-to-fourteen modulation?
It is the channel code used for the audio compact disc (CD).
Name two common audio compression formats.
MP3 and AAC are common compressed formats; FLAC is a lossless format.
What is sample-rate conversion?
It is the process of changing the sampling rate of a digital signal, including upsampling and downsampling, to match a common rate.
How does digital audio reduce distribution costs?
Digital audio can be distributed as data files over the internet, reducing the need for physical copies like records and tapes.
What is the role of a transducer like a microphone in analog audio?
A microphone converts physical sound waves into electrical representations of those waveforms.
What is the main difference between analog and digital audio signals?
Analog signals are continuous waveforms susceptible to noise and distortion, while digital signals are discrete numerical samples that can be error-free.
What happens if a disturbance occurs in a digital system?
Disturbances do not result in error unless they are large enough to misinterpret a symbol or disturb the sequence of symbols.