The physics of Bose speakers

No gadget maker perhaps understood soundwaves as well as Amar Gopal Bose did. The author reveals the science behind the innovative engineers products

In the 1950s, Amar Gopal Bose, realised that there was more to the science of sound than the reproduction of audio waves. The ear translates sound waves into neural signals and sends these to the brain. The brain processes the neural signals in its own peculiar ways. There are noises the brain wont hear, even within the normal human auditory range. There are also ways to trick the brain into hearing phantom sounds.

Bose, an engineer of astounding ingenuity, parlayed that primary insight about audio perception into a lifetime of designing smaller and better sound-processing equipment. In many ways, he founded the science of psychoacoustics the study of sound perception.

Music sounds better in enclosed spaces because, for some evolutionary reason, the brain finds it pleasurable to process reflected sounds, with all its harmonics and sub-harmonics. We know this instinctively. Even the most tuneless among us indulges in the guilty pleasure of bathroom singing.

Similarly, for this very reason, music played in opera houses and auditoriums sounds better. In the best auditoriums, up to 90 per cent of what is heard is reflected sound. However, when Bose started his research, this knowledge had not translated into design. Sound equipment delivered direct sound with the entire output aimed at the listener.

Bose figured out ways to reproduce reflection effects on small scales. His classic 901 series of speakers was the breakthrough. Released in the late 1960s, it set industry standards for over 20 years. The 901 featured nine small embedded speakers inside each box. Eight of those were aimed to reflect off walls while only one aimed directly at the listener. It was the first time that people sitting at home heard music that made them feel as though they were sitting in an auditorium. This wasnt the only speaker-related innovation Bose came up with, of course. He was a genius at miniaturisation, creating ever-smaller devices with fantastic sound.

Another big insight led to the development of effective noise-cancelling headsets. The legend goes that Bose was on a long flight circa 1978 and trying to listen to music on a headset over the roar of the engines. By the time the flight ended, he had sketched out prelim designs and specifications for active noise-cancellation equipment.

Active noise cancellation relies on a simple principle. Sound waves have a certain amplitude and frequency. If that is decoded, an anti-wave with the same amplitude and frequency that is 180 degrees out of phase can be generated. Then the two waves cancel out and youre left with silence.

Understanding the principle is easy. Designing circuitry to decode ambient noise and to generate anti-waves on the fly is not so simple. Making that circuitry small enough to fit in the ear is even more difficult. Bose cracked it and reset industry standards in the process.

Apart from this, the innovative use of waveguides led to the Bose Wave range. A waveguide is any V-shaped device that guides and constricts sound waves, such as a megaphone, for example. In the mid-80s, Bose and his collaborator, William Short, created a radio set where embedded small waveguides pushed out full stereo through woofers. That was the first Bose Wave system now a sophisticated range of ghetto-blasters accepting inputs from multiple sources.

One project Bose left unfinished is intriguing. After a five-year study, he designed an automobile suspension system that supposedly has magnitudes better than standard. Auto suspensions do two things offer comfort and control. Those two goals are in conflict, using standard shocks and springs. If feedback from the wheels is damped for comfort, control is reduced.

Bose suspension uses electromagnetic motors and amplifiers attached to each wheel. Algorithms decode vibrations as the car moves, and sends back anti-signals to control those vibrations. This system actually regenerates electricity, while allowing incredibly good control and high comfort levels. Unfortunately, its very expensive and only available in very high-end custom vehicles.

Bose fans will not be surprised.

The great inventors gear was never cheap but always value for money. People scrimped and saved to buy his systems. The suspension system too, may end up becoming more mass-market as its adopted, first by luxury marques and then in larger scales. Thats pretty much what happened with Bose audio systems. Maybe in the not-too-distant future, we can dream of driving with perfect comfort and control down dirt tracks in cars equipped with Bose suspensions, as we listen to wonderful music on our Bose systems.