![]() ![]() This allowed me to create a suite of filters which could be separately configured for the left and right channels (since as observed in Figure 2, the characteristics of the noise peaks varies between the channels). However, rather than using Ableton Live’s notch filtering as I did last time, I used MATLAB. Suppressing the “power hum”Īs last time, notch filtering was used to suppress the low-frequency peaks from Figure 2. Also, there is a distinct peak around 1150 Hz in both channels and a lesser peak around 1700 Hz in the left channel only. Interestingly, the low-frequency power hum (Figure 2) comprises only the fundamental mode (at approximately 60 Hz) rather than the multiple harmonics observed last time. The noise has similar characteristics to the last time: some low-frequency “power hum” (Figure 2) plus a broad-band “tape hiss” over the extent of the audio/music bandwidth (Figure 1). Figure 2: Noise spectrum, zoomed-in on the low-frequency regime, revealing the 60 Hz “power hum” plus a distinct peak around 1150 Hz in both channels and a lesser peak around 1700 Hz in the left channel only. Figure 1: Noise spectrum revealing the broadband nature of the background noise in the recording. Snippet of the raw (noisy) recordingįigures 1 and 2 show the noise spectrum (over the full bandwidth and zoomed-in to the low-frequency zone, respectively) computed via the MATLAB pspectrum function. Here is a clip of the lead-in to the show. In this post, I explain how I cleaned it up using a more elaborate technique than previously.Īgain I used MATLAB for the algorithm development aspects of the process, in combination with Ableton Live for the audio and mix management. Again from an old cassette tape, this recording is rather noisy. I’ve since received another old Havering recording from Walt. Last time I wrote about audio restoration using simple digital filtering (in MATLAB and Ableton Live).
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