A waveform describes a value changing over time. At an analog input, that value is a voltage; in digital audio, it is a sequence of samples. Amplitude describes the size of the displacement. Frequency is the number of cycles per second, measured in Hz. The period is T = 1/f; at 100 Hz, one cycle takes 10 ms.
A simple sine wave can be written as x(t) = A sin(2πft + φ). A sets amplitude, f sets frequency, and φ sets phase. Phase describes a position within the cycle; similar signals can reinforce or reduce each other when combined. A polarity flip reverses the sign of every sample. It does not shift the signal in time as a delay does.
A guitar is not a single sine wave. One note contains a fundamental, harmonics, a transient, and noise. These components add together into one waveform on a channel. A spectrum is a way of viewing their frequency contributions, rather than a collection of separate audio cables. Two signals with similar amplitude spectra can have different waveforms because their phases differ.
Phase and parallel summing
Why can a merge get louder or disappear?
- Sum Peak
- 2.000×
- Relative to Peak A
- 6.02 dB
- B polarity
- Normal
A merge sums signals. Output level can rise or fall even when each branch level stays unchanged.
Two sine waves at the same frequency. Equal levels with a 180° phase difference cancel. Delaying a complex sound can create comb filtering, rather than just one phase angle.