# Sounds A Level Resources

## A Level Computer Science: Sounds

Do you want to save hours of lesson preparation time? Get your evenings and weekends back and focus your time where it's needed! Be fully prepared with presentations, notes, activities, and more.

All Computer Science topics are covered, and each module comes complete with:

Classroom Presentations
Revision Notes
Activities & Quizzes
Mind Maps, Flashcards & Glossaries

#### What is the difference between lossy and lossless compression in sound files?

Lossy and lossless are types of compression algorithms used for sound files. Lossy compression reduces file size by eliminating some audio data, which results in a loss of sound quality. Examples include MP3 and AAC formats. On the other hand, lossless compression maintains the original audio quality while reducing the file size, although not as drastically as lossy compression. Formats like FLAC and WAV are examples of lossless audio files.

#### How does sampling work in storing sound on a computer?

Sampling is the process of converting a continuous analog sound wave into a series of discrete digital values that can be stored and manipulated by a computer. In this process, the sound is sampled at regular intervals, usually thousands of times per second, and each sample is turned into a binary value. The rate at which these samples are taken is known as the "sampling rate," usually measured in Hertz (Hz).

#### What is Nyquist’s Theorem and why is it important for audio?

Nyquist's Theorem states that a continuous signal can be completely represented by its samples and fully reconstructed if it is sampled at more than twice the highest frequency present in the signal. For audio, this means that the sampling rate must be at least twice the highest frequency in the audio file to accurately represent the original sound. Failure to do so can result in aliasing, where higher frequencies get mapped into lower frequencies, distorting the sound.

#### What are MIDI files and how are they different from other audio files?

MIDI (Musical Instrument Digital Interface) files don't store actual sound data but rather contain instructions that tell a musical instrument or computer software how to produce the sounds. They are more like a digital sheet music than a recording. This makes them significantly smaller in size compared to other audio formats like MP3 or WAV. MIDI files are commonly used in composing music, synthesizers, and other musical applications.

#### How is the size of an audio file calculated?

The size of an audio file can be calculated based on multiple factors such as the sampling rate, bit depth, and the duration of the audio. The formula to calculate the file size is usually:

File Size=Sampling Rate×Bit Depth×Number of Channels×Duration in seconds

Bit depth refers to the number of bits used for each sample, and the number of channels indicates whether the audio is mono, stereo, or multi-channel. The resulting size might further be reduced through compression algorithms.