Multimedia - Sound — common mistakes

Examiners love file size calculations. Always show your full working, including the formula. Pay close attention to units: convert kHz to Hz, minutes to seconds, and be careful when asked for the final answer in bytes, KB, MB, or GiB. Remember that 1 KB = 1024 bytes, not 1000, unless the question specifies otherwise.

It's a trade-off between quality and file size. While higher rates and resolutions produce better quality audio, they also create significantly larger files. This has major implications for storage space and transmission bandwidth, especially for streaming services or portable devices. The chosen settings are often a compromise to achieve 'good enough' quality for the intended purpose with a manageable file size.

They are related but distinct. Bit depth (or sampling resolution) is the number of bits per sample (e.g., 16-bit). Bit rate is the total number of bits processed per second (measured in bps or kbps). You can calculate the bit rate for uncompressed audio using: Bit Rate = Sampling Rate × Bit Depth × Number of Channels. So, bit depth is a component used to calculate the overall bit rate.

The principles of sampling and quantisation are the foundation for all digital audio, including MP3s. However, the file size calculation formula only works for uncompressed audio like WAV or AIFF. MP3 is a compressed format that uses clever algorithms to remove data that humans are unlikely to hear, resulting in a much smaller file size than the formula would suggest.