There are two main types of noise: 1) impulse noise, and 2) continuous noise.

Examples of impulse noise are pops, clicks and crackle.

Pops and clicks occur in modern audio production for film, television or music - not just in phonograph recordings. A poor electrical connection, a minor fault in digital audio transmission, or a single hand clap can cause serious production problems.

Continuous noise includes tape hiss, air conditioning, traffic noise, continuous surface noise of old recordings, AC hum and buzz, motor whine, etc.

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How Is the Noise Removed?

Historically, impulse noise has been removed by waveform reconstruction using sophisticated interpolation techniques. Normal audio passes through the system unaltered, and only when a pop or click is detected does waveform reconstruction occur.

We have an extensive collection of CEDAR Cambridge processes, including the De-click process. However, some clicks and pops manage to elude detection and correction, so manual de-cllicking is sometimes required as a follow-up. For small areas requiring more work, we use CEDAR Retouch.

We use CEDAR Cambridge NR-5 to remove hiss and broadband noise. The NR-5 process divides the audio spectrum into thousands of individual segments and applies downward expansion in each segment based on the presence of program material in comparison to a noise sample.

Much of the power of CEDAR Cambridge NR-5 to remove broadband noise is based on its ability to tailor its algorithm to specific conditions. A sample of the noise is captured and a detailed frequency analysis is performed. The result is used to model the offending noise.

We remove motor noise, hum and buzz using CEDAR Cambridge Debuzz process and other adaptive processes.

More than one process is usually required.

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How Long Will It Take?

We don't know! Every situation is different. Even though most processing takes place in real time, minor adjustments are quite important, and it takes operator skill and care to achieve best results.

Depending on your source material and your requirements, noise removal can done be quickly, or it can take many multiples of source material running time. In very simple cases, noise reduction can be accomplished as your material is loaded onto the workstation for CD mastering. In difficult cases, some manual de-clicking or non-real time computer processing will be required to obtain proper results. This can take some time.

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How To Submit Material?

Whether your material is submitted in analog or digital format, you should do the following (if possible):