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Sound Wave Lab

How an analogue sound wave is turned into digital data by sampling, and how the sample rate, bit depth and duration set the file size and quality of a recording.

⏱️ 15 min 🎯 13 activities Teachers Not yet rated Students Not yet rated

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What you'll cover

From sound wave to bits 🔊

A microphone turns a sound into an **analogue** signal: a smooth, continuously changing wave. Computers can only store **digital** data, so the wave has to be turned into numbers. In this lab you will learn how **sampling** captures a sound wave as binary, and how to work out the **file size** of a digital recording.

The sampling words 🔑

The key ideas for digitising sound:

Digitising a sound wave 🪜

An interactive activity.

Match the terms 🔗

  • Sample rate
  • Bit depth
  • Sample interval
  • Amplitude
  • The number of samples taken per second
  • The number of bits used for each sample
  • The time between two samples
  • The height of the sound wave at a point

Measuring the rate 📏

What is the sample rate of a sound recording measured in?

  • Hertz, the number of samples per second
  • Bits per sample
  • Seconds
  • Pixels

The file-size formula 💡

The size of a sound file depends on three things: **file size = sample rate x bit depth x duration** Use the sample rate in hertz, the bit depth in bits, and the duration in seconds. The answer is in **bits**. To convert to **bytes**, divide by 8.

Work out the file size 🧮

An interactive activity.

Bits to bytes ➗

An interactive activity.

Quality vs file size ⚖️

Increasing the sample rate or the bit depth captures the sound more accurately, but makes the file bigger.

Bigger file, better quality ✅

Select the TWO changes that would BOTH improve the sound quality and increase the file size.

  • Increasing the sample rate
  • Increasing the bit depth
  • Making the recording shorter
  • Using fewer bits per sample

The process in words 🧱

To digitise sound, the computer takes a _____ of the wave at regular intervals. The number of samples per second is the _____, measured in hertz. The number of bits stored for each sample is the _____. A higher sample rate gives better _____ but a larger _____.

sample sample rate bit depth quality file size pixel resolution colour depth smaller analogue

Set up the recording 🎙️

An interactive activity.

Explain and calculate ✍️

An interactive activity.