The Digital Audio Quiz! MCQ Trivia

See the explanation for the previous question. Blumlein was an early sound engineer who demonstrated that a stereo recording could be made with 2 microphones in a suitable pattern. He is nothing to do with digital audio, however. Einstein was a famous theoretical mathematician and physicist and Wittgenstein was a philosopher.

In digital audio, the anti-aliasing filter usually filters out anything above 20kHz which ensures that there are at least 2 samples to encode the highest frequency if the sampling rate is above 40kHz. (e.g. 44.1 kHz)

The more numbers you have the louder you can record. Engineers usually go for at least 24 bits at the tracking stage even though it has to be re-clocked to 16 bits on transfer to CD.

Aliasing is a phenomenon whereby false (alias) frequencies are created when there are not enough samples to fully represent the waveform. A visual form of aliasing is the illusion of wagon wheels going backward in Westerns. The sampling rate of film is around 30 frames per second.

This rounding is called quantisation error and it is where most of the noise comes from in digital audio.

The sampling process chops the audio up into discrete measurements, which are quantized in time by the sampling rate (E.G. 44.1kHz) and in amplitude by the number of bits (E.G. 16 bits) The sampling rate affects the bandwidth and the bit depth affects the dynamic range (noise level)

The greater the sample rate the higher the frequency that can be allowed into the system. If you sample at 32kHz your audio will have to be filtered to around 15 kHz. (e.g. FM radio)

Half the sampling rate is sometimes called the Nyquist frequency after the Swedish mathematician who demonstrated that it takes 2 samples to represent a frequency and that less than this will produce alias artifacts.

Quantization noise is the unwanted effect that can occur when the bit depth is low. When the bit depth is low, there are fewer levels available to represent the analog signal, resulting in a loss of detail and accuracy. This loss of detail leads to quantization errors, which manifest as quantization noise. This noise is perceived as a distortion or background noise in the digital signal, reducing the overall quality of the audio or image.

The AAF first limits the bandwidth to something that the sampling rate can cope with, then the numbers are generated by sample and hold. The signal is now digital and can be processed and edited. After this, on playback, the numbers are converted back to a digital wave which is then filtered (Data recovery) to remove the spurious high frequencies and smooth the waveform to completely recover the original audio.

D Would yield very lo fi audio. A is the current minimum standard. B and E are becoming increasingly popular.