Learn English – What’s the term for “seeing” words when you hear spoken language

Making my comment into an answer

"Legend has it .."

However, the dictionary for legend says

An unverified story handed down from earlier times, especially one popularly believed to be historical.

and though the phrase above works, I feel legend implies a story or a fable, rather than the sayings which the original question mention.

I would suggest:

(1) input gain mismatch or input gain shift. Since this is describing the technical aspect, the effect is caused by either of:

1. Switching to an input source with a different impedance, or pre-amp level output. The final amplification has no way to discern the amplitude increase that will result. Also contrinuting to this is that [now obsolete] mechanical contacts will arc as they seperate creating an input voltage spike "pop".

2. Variations in the headroom of recorded material. All analog signals are recorded to a scaled reference ranging from -infinity decibles to 0 decibels, with 0 dB being the "loudest". That is loudest in proportion to the amplifiers capability before going into saturation, or overshooting (+dB) the maximum capability of the amplifier to reproduce and amplify without distortion. A great recording should get close to 0dB headroom only on its loudest peak moments. Without care, another recording might have lots, or perhaps too much headroom, which will be distortion free, but have a limited dynamic range (difference bewtween the quitest and loudest passages)

(2) startled : cause (a person or animal) to feel sudden shock or alarm. "a sudden sound in the doorway startled her"