# E7H02 - What is a microphonic?

**URL:** <https://forum.openhamprep.com/t/e7h02-what-is-a-microphonic/1424>\
**Category:** Extra Questions\
**Created:** [January 2, 2026, 7:53pm UTC](https://forum.openhamprep.com/t/e7h02-what-is-a-microphonic/1424 "2026-01-02T19:53:28Z")\
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**Author:** ![system](https://forum.openhamprep.com/uploads/default/original/1X/a8bc13ef992b522befd6b1d923d2f2a53605a9c7.png) [@system](https://forum.openhamprep.com/u/system)\
**Post date:** [January 2, 2026, 7:53pm UTC](https://forum.openhamprep.com/t/e7h02-what-is-a-microphonic/1424/1 "2026-01-02T19:53:28Z")

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## Question

What is a microphonic?

## Answer Options

- **A)** An IC used for amplifying microphone signals
- **B)** Distortion caused by RF pickup on the microphone cable
- **C)** Changes in oscillator frequency caused by mechanical vibration
- **D)** Excess loading of the microphone by an oscillator

**Correct Answer: C**

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## Explanation

In sensitive electronic circuits, particularly high-frequency oscillators and amplifiers, unwanted noise can be introduced by mechanical means. Physical vibration or shock can cause component leads, circuit board traces, or internal wiring to flex or change position slightly.

**Microphonics** is the term used to describe **changes in oscillator frequency caused by mechanical vibration** (or acoustic energy). When a component or wire moves, its parasitic capacitance or inductance changes, which slightly shifts the resonant frequency of the oscillator tank circuit. This results in frequency instability that appears as modulation or jitter on the signal.

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