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Sound Tests & Test Tones Tests your Audio Equipment, Room Acoustics and Hearing, online

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F.A.Q. Frequently asked questions.

Swept Sine (Lower Spectrum)

Background

These audio files scan the lower range of audible frequencies, from 20Hz to 200Hz in a 10s time span.

When the time scale is logarithmic, sweeping between 20Hz and 40Hz (one octave) or from 100Hz to 200Hz (one octave) will take the same time. When the time scale is linear, sweeping from 20Hz to 40Hz will be much faster, and equal to the time taken to sweep from 100Hz to 120Hz (3 semitones).

Applications

Use these files to determine resonant frequencies in your room. These resonances occur in every enclosed space. Sound waves are bouncing from the walls, ceiling and floor and interact with the original wave and between themselves. At given frequencies, this interaction is stronger than others (standing waves). The frequency of each resonance is directly related to the room's dimensions (room modes). When you play a sound having the same frequency as a natural resonance of the room, that note will sound much louder (constructive interference), or weaker (destructive interference) depending on your listening position.

20Hz-200Hz swept sines can also be used to check the transition between your subwoofer and main speakers.

The sound files

As you play the file, pay attention to sudden changes in level. In this frequency range, those changes can only be due to room resonances, or - if you use a subwoofer - to a mismatch between the subwoofer phase/position/crossover frequency and your main speakers.

External Links

• Room acoustics @ U. of Salford
• Room modes crash course
• Room Mode Calculator
• Setting-up your subwoofer