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Three general classes of noise are found on sound recordings: clicks, crackle and hiss. Cool Edit Pro has a number of FFT filters which deal specifically with these problems.

Click/Pop Eliminator

Click/Pop Eliminator
Removing clicks and pops using Cool Edit Pro.

The Click/Pop Eliminator works by searching for anomalies in the audio data that could be construed as clicks or pops (Detection), and then replacing or repairing the damaged location (Correction). It’s more accurate than just cutting out the click, or replacing the data with a straight line. This filter was not used to deal with reel-to-reel recordings, but was invaluable in dealing with 78rpm disc recordings.

Noise Reduction

Noise Reduction
Removing unwanted noise using Cool Edit Pro.

Cool Edit Pro’s Noise Reduction function can dramatically reduce background and general broadband noise with a minimal reduction in signal quality. It can also remove tape hiss, microphone background noise, 60 cycle hum, or any noise that is constant throughout the duration of your waveform. This was used to remove background noise from both tape and disc recordings.

Hiss Reduction

Hiss Reduction
Removing hiss using Cool Edit Pro.

The Hiss Reduction facility was used to remove annoying hiss from nearly all recordings. It removes all audio in all frequencies that are below a certain threshold (which is generally the noise floor or hiss level). If audio has a constant background hiss, then that hiss can be “noise gated” or removed completely. Any audio in any frequency band louder than the cutoff level will remain untouched. This filter was often applied after all other noise reduction and audio editing had been completed. In most instances this gave a better result than where hiss reduction had been applied earlier in the process.

The net aural effect of removing noise from sound recordings can be spectacular. Judicious use of digital noise reduction can effectively free music from the shortcomings of its recording medium, uncovering details which were once masked by noise. Overuse of noise reduction filters can result in the introduction of new distortions. Distortion effects may manifest themselves a “hollow” or “underwater/burbley” sounding signal, dull sounding impacts, “rolly” high end, or a “computerish” mechanical sound. These effects, if heard at all, will fall off if the noise reduction level is reduced. The amount and type of distortion depends on the type of noise that is being filtered. Digital noise reduction is a tricky balance between retaining the integrity of the original recording and producing audio that is both useful and pleasant to listen to.

Few of the recordings are of studio quality and most were made in less than ideal circumstances. Often the background chatter of a noisy pub recording, or the loud ticking of a mantelpiece clock can be louder than the music, speech or song that we are interested in. The filters listed above along with dynamics processing and EQ were often used to deal with these problems.







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STEP BY STEP GUIDE



Stage - 1
Stage - 1
Playing the original tapes using an AKAI GX 4000DB tape deck

Stage - 2
Stage - 2
Digitizing the analogue signal using soundMAX integrated digital audio

Stage - 3
Stage - 3
Reducing the background noise using fft filters

Stage - 4
Stage - 4
Editing using Cool Edit Pro

Stage - 5
Stage - 5
Creation of Mp3 files

Stage - 6
Stage - 6
Encoding for the Internet using RealNetworks Helix Producer plus 9


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Prince Consort Road, Gateshead, NE8 4LN
Tel: 0191 433 8430