# Pitch and loudness

Pitch is how high or low a note sounds and depends on frequency. Loudness depends on amplitude. Humans hear about 20 Hz to 20,000 Hz.

Physics (school) · Part 05: Waves, sound and light · Card 8 of 8 · Last updated 2026-10-19

## Analogy

A small guitar string sounds high and thin. Hitting it harder makes it louder, not higher.

## Example

**Reading an oscilloscope**

Higher peaks = louder (amplitude).
More waves in the same time =
higher pitch (frequency).

## In practice

Ultrasound is above 20,000 Hz. Doctors use it to scan unborn babies.

## Practice

### Flashcards

- **What does frequency control in a sound?** Its pitch.

## Questions people ask

### What is ultrasound?

Ultrasound is sound with a frequency higher than 20,000 Hz, which humans cannot hear. It reflects off boundaries between different materials, so a machine can use the echoes to build a picture. Doctors use it to check babies in the womb without using harmful radiation.

### Why do some animals hear sounds we cannot?

The range of hearing differs between species. Humans hear roughly 20 Hz to 20,000 Hz, but dogs can hear much higher frequencies, and bats use ultrasound to find insects in the dark. A dog whistle makes a sound too high for a person to hear.

## Related concepts

- [Sound](https://studyvisually.com/learn/science/physics-school/physics-school-part-5/physics-school-part-5-concept-7)
- [Waves](https://studyvisually.com/learn/science/physics-school/physics-school-part-5/physics-school-part-5-concept-1)
- [Amplitude, wavelength and frequency](https://studyvisually.com/learn/science/physics-school/physics-school-part-5/physics-school-part-5-concept-2)
- [Wave speed equation](https://studyvisually.com/learn/science/physics-school/physics-school-part-5/physics-school-part-5-concept-3)

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