Web graphs and listening online

Regarding audio playback and the online listening experience

Before playing the online noise data graphs, it is vitally important that you understand while listening to the audio that you are hearing an example of the character of the noise and not an exact replication of the noise recorded. This is similar to how a photo gives you a visual representation of an object.

There will be differences compared to the original noise because of the following reasons:

  1. The audio is usually recorded with a sound level meter in a single channel (mono). A real world experience would have inherent directionality (binaural stereo).
  2. The character of the reproduced audio will be changed depending upon the quality of your audio system (e.g. sound-card, amplifier, speakers) and the environment that you are in.
  3. It is not easy to ensure the output loudness is set to the correct decibel level without expensive equipment.
  4. You should make yourself aware of other sources of noise around you, such as from your computer, which can add interference.
  5. Interference may sometimes exist within the audio file itself. This will occur when the recording was done in a low-level environment, without the correct equipment such as a low-noise microphone, and therefore electrical and instrument noise or the noise floor of the audio file itself influences the output.
  6. Distortion may sometimes exist within the audio file itself. “Clipping” will occur when the sound level was above the range of the audio file. This can even be due to infra-sound, i.e. sound waves at inaudibly low frequencies but still detected by the microphone and saved to the audio file. Distortion can also occur when the audio is recorded at a low sample rate and/or bit rate.

Playback through speakers will give you more of the sense of listening to the noise in the real world however if you have computer noise, are not in a quiet environment or do not have high quality speakers then it is best to use headphones.

Playback through headphones may reduce noise from your surroundings and give you more of the lower frequencies but it can sound unnatural as playing a mono signal directly into both ears loses the sense of direction and space.

It is advisable to give your ears time to adjust to the sound. For short clips it might be worthwhile to play them through a few times. The perception of sound level adjusts to its environment so if you have come from a noisy environment you may find that your experience changes as your hearing, or more precisely your perception of sound, adjusts.