The “BRAIN” Model of Intelligibility in Business Telephony

There are times when there is no substitute for being understood on the telephone. Well before 1937, the limitations of the telephone in accurately conveying speech were known. Irregular and limited bandwidth, noise, variations in end-to-end loudness, sidetone, and distortion had all been identified as contributors to degradation of the spoken word. In 1910, Campbell performed experiments in which he found 59 percent accuracy when words were called over the telephone, as compared to 96 percent through open air. The abilities of the telephone as an efficient and accurate channel for human speech have always been regarded with a bit of a wink and a chuckle, tolerated due to a common understanding that it is the best available.
Despite modern digital trunking and switching technology, this remains an everyday problem. Why? Analog loop lengths, building wiring, variable line equalization characteristics, poor handset and speakerphone designs, mixed networks, noise in conference rooms, paper shuffling, pen tapping, fan noise, and a host of other issues are still with us, even here in the digital age.
This paper discusses these issues and presents the “BRAIN” model of critical elements in business telephony. We show how their mutual dependencies can be used to improve telephone and audio system performance, and how contemporary systems can produce direct benefits to clear communications.