Digital music starts as changing air pressure that our ears hear as sound. A microphone turns those pressure changes into an electrical signal, and a computer measures that signal many times per second. Each measurement becomes a number, so the smooth sound wave can be stored as digital data.
This matters because every song on a phone, laptop, or streaming app is really a carefully organized pattern of numbers.
Key Facts
- Sample rate tells how many times per second the sound wave is measured, such as 44.1 kHz = 44,100 samples per second.
- Bit depth tells how many possible loudness values each sample can store, such as 16 bit = 65,536 possible values.
- Uncompressed file size in bits = sample rate × bit depth × number of channels × time in seconds.
- CD-quality stereo audio is often 44.1 kHz, 16 bit, and 2 channels.
- WAV is usually uncompressed, FLAC is lossless compressed, and MP3 is lossy compressed.
- Higher bitrate usually means better sound quality and larger file size, such as 320 kbps being larger than 128 kbps.
Vocabulary
- Sample rate
- The number of sound measurements recorded each second when converting audio into digital data.
- Bit depth
- The number of bits used to store each audio sample, which affects how precisely loudness can be represented.
- Binary
- A number system using only 0s and 1s that computers use to store and process data.
- Compression
- A method of reducing file size by storing audio data more efficiently or by removing some information.
- Bitrate
- The amount of digital audio data used per second, often measured in kilobits per second.
Common Mistakes to Avoid
- Confusing sample rate with bitrate is wrong because sample rate is how often the wave is measured, while bitrate is how much data is used each second.
- Thinking MP3 and WAV store sound the same way is wrong because MP3 usually removes some audio information to make a smaller lossy file, while WAV often keeps the full uncompressed data.
- Assuming higher file size always means noticeably better sound is wrong because speakers, headphones, listening environment, and human hearing limits also affect what you can hear.
- Forgetting stereo has two channels is wrong because file size calculations must multiply by 2 for left and right audio channels.
Practice Questions
- 1 A mono audio file is recorded at 44,100 samples per second with 16 bits per sample for 10 seconds. How many bits of data are stored before compression?
- 2 A stereo song is streamed at 128 kbps for 3 minutes. About how many kilobits of data are transferred? Then convert your answer to kilobytes using 8 bits = 1 byte.
- 3 A student says a FLAC file and an MP3 file sound different only because one is louder. Explain why the file format and compression method can affect audio quality even when both files are played at the same volume.