Physics · New

Sound Waves: Two Speakers & Interference

Play a note through two speakers, drag a listener around the room and find the loud and silent spots.

Interactive 100% free No signup Works on phones

Two speakers play the same note. Where their waves meet in step you hear a loud spot, and where they meet out of step you hear silence. Drag the listener (or the speakers) around the room to find them.

Sound Waves: Two Speakers & InterferenceAZRS Sims

Wavelength–

Path difference–

Loudness at listener–

At the listener–

Frequency–

About the Sound Waves: Two Speakers & Interference

Free sound waves: two speakers & interference. Play a note through two speakers, drag a listener around the room and find the loud and silent spots. Drag, change the sliders and see the result live. No sign-up, works on phone and computer. Built for physics, the sound waves: two speakers & interference runs instantly in your browser: change a setting or drag an object and the result updates at once, so you learn by trying things out rather than only reading about them.

Play a note through two speakers, drag a listener around the room and find the loud and silent spots. Use it to explore physics ideas at your own pace, then check what you found against the key ideas further down this page.

How to use the Sound Waves: Two Speakers & Interference

Use the controls to change Frequency, Speaker separation, Second speaker, Colours. The simulation reacts instantly.
Pick an option such as In phase, Out of phase, Off, Red / blue to switch modes or load an example.
Where you see a glowing handle, object, weight or atom, drag it with your mouse or finger. Everything responds in real time.
Watch the readouts and graphs update as you experiment, and compare what you see with the key ideas below.

Things to try

Move the listener along a line and find the quiet spots.
Change the second speaker to out of phase.
Raise the frequency and see the pattern get finer.

Key ideas you can learn

Two waves add where they arrive in step (loud).
They cancel where they arrive half a wavelength apart (silent).
Path difference decides what you hear.
Noise cancelling headphones use destructive interference.

Where this is used in the real world

Concert halls, speaker placement, noise cancellation and radar all use wave interference.

Who is this simulation for?

Physics students in middle school, high school and first-year university, teachers who want a quick demonstration for the projector, and anyone revising for exams. It works well for flipped classrooms because students can explore before the lesson.

For teachers: project it on the board, let students predict what will happen, then run it together. For students: change one thing at a time and write down what changes.