---
title: "Harmonic"
description: "A harmonic is an integer multiple of a fundamental frequency. A 75 Hz sonic horn radiates energy at 75 Hz (the fundamental, also called the first harmonic), with smaller amounts at 150 Hz (second harmonic), 225 Hz (third), and so on. The harmonic spectrum is what gives a real horn a richer, less pure tone than an idealised single-frequency source."
canonical_url: "https://sylio.co/glossary/harmonic"
last_updated: "2026-06-28T02:29:22.636Z"
---

A **harmonic** is an integer multiple of a [fundamental frequency](/glossary/fundamental-frequency). A 75 Hz [sonic horn](/glossary/sonic-horn) radiates energy at 75 Hz (the fundamental, also called the first harmonic), with smaller amounts at 150 Hz (second harmonic), 225 Hz (third), and so on. The harmonic spectrum is what gives a real horn a richer, less pure tone than an idealised single-frequency source.

## Why harmonics matter in cleaning

Most of the cleaning work is done by the fundamental, because energy is concentrated there. Harmonics extend the effective frequency content of the horn, which can be helpful where the vessel contains internals with mixed resonant characteristics — a horn nominally rated at 75 Hz also contributes some cleaning at higher harmonic frequencies useful for finer dust pockets.

## Why harmonics matter in vibration analysis

Plant vibration teams analysing tube banks, fan shafts or duct supports look for energy at the horn fundamental *and* its harmonics. Avoiding overlap with structural [resonance](/glossary/resonance) modes is part of multi-horn installation design.

## Related terms

- [Fundamental frequency](/glossary/fundamental-frequency)
- [Frequency](/glossary/frequency)
- [Resonance](/glossary/resonance)
- [Octave band](/glossary/octave-band)