There is something missing in Iqbal Bano’s haunting melody Dasht-e-Tanhai and The Beatles’ hit Love Me Do — pure clarity. The reason: these songs were recorded before the advent of Dolby technology. A subtle hiss, primarily caused by electrical noise, was common in songs recorded in the studio before the 1970s. The sound was a grave annoyance for the artists, and more so for music lovers.
It required a genius like Ray Dolby, an electrical engineer and a music aficionado, to step in and change the way we listen to music today. He pioneered noise reduction technology, audio compression that brought down the hiss. Initially meant for professional recordings, it was later introduced for consumer products. Ray died of leukaemia on September 12 this year.
For more than four decades, Dolby Laboratories, which was set up in 1965, has been a pioneer in the fields of music recording and film sound. Like Amar Bose, who died in July, Ray was an inventor-entrepreneur who noticed and solved a subtle problem that has had a profound impact on the music and film industries.
Suppressing the noise
Unnecessary ‘information’, be it the ‘hiss’ in the audio, the grainy spots on an image, or the more common ‘chatter’ in a recorded conversation, are the noises we deal with on an everyday basis. Dolby Laboratories specialised in the art of suppressing electrical noise, which appears as a hiss, most prominently during the ‘silent’ phases of an audio recording. This electrical noise is due to the unrest in electrons and the laws of physics imply that this cannot be prevented, only cured.
Ray originally devised his electrical filters, which could perform the threshold filtering of signals, in the early 1970s in a product that became the de facto standard for audio recording. The first noise reduction filters ‘Dolby A’ worked on a basic signal processing concept that uses pre-emphasis and de-emphasis in a dynamic way. In this technique, signals from all frequencies, barring those below a certain threshold, were sent through filters during the recordings.
The hiss that was present at low amplitudes was thus dealt with, without tampering with signals of higher amplitude. During playback, de-emphasis is performed again on the low amplitude signals and then added back to the high amplitude signals. In essence, only low amplitude signals, or silent passages in music were processed, while the high amplitude signals like a piano section would pretty much be untouched.
Capturing the entire spectrum
A pervasive problem when listening to music recorded on tape was that the players would work well with low amplitude signals, but there would be distortion of loud and high frequency signals such as a recoding of a violin. This was an indication of low performance recording in a dynamic range, which is the range between the faintest and the loudest signals that can be recorded and played back. This range for the human ear is about 1,00,000 times. Human ears have the ability to hear a clock tick, and also the loudest of sounds in a music concert. This extensive range cannot be faithfully recreated by audio recording.
Ray solved this problem in 1985 with intelligent use of compression and decompression. In Dolby Spectral Recording, a wide range of signal levels could be accommodated into recordings by recording different bands of frequency differently, hence increasing the dynamic range of audio recording substantially.
Dolby Digital transformed the audio experience in cinemas. In fact, it enabled much of what modern music is capable of delivering to audiences.
Noise reduction and distortion avoidance in music recording were problems that had existed ever since recording if music began. If Ray had only been an electrical engineer, these problems would not have been solved. But, he was a keen lover of music, which enabled him to use the laws of physics to make music sound like never before.
