In a sense, the name of the game in audio has been "more signal for less noise." All the formats for storing and reproducing sound have built-in noise levels, and a major thrust by engineers has been to minimize the inherent noise while optimizing the signal imposed over it.

Efforts in this area have been legion. Most sound enthusiasts are familiar with filters, noise suppressors, volume expanders and so on. More recently we have seen a trend to new recording techniques such as direct-to-disc and digital sound processing.

Two very new developments were revealed at the recent Consumer Electronics Show in Chicago. One is a novel twist to the Dolby noise-reduction system; the other is a modified disccutting technique developed by a firm called "dbx."

The Dolby idea, known as HX, extends the recording signal "headroom" in conjunction with regular Dolby-B noise-reduction in a cassette recorder. It permits recording at frequencies of 10,000 Hz and above with levels that are at least 10 decibels higher than is presently available. At the same time, the response at low and middle frequencies is said to be improved for minimal distortion, modulation noise and dropout effects.

Dolby HX works by automatically varying a recorder's bias and equalization to suit the changing signal levels being taped, while avoiding saturation of the tape. It can be used with any kind of tape for which a given recorder is adjusted. Once a tape has been so recorded, it can be played back with the conventional Dolby system.

Adding "HX" to a cassette recorder is still a job for the manufacturer. Dolby says the new parts will add about one-third to the cost of present Dolby circuitry. Existing Dolby licensees will not be charged additional royalty or licensing fees for HX.

The dbx system involves the cutting of a master disc regardless of how the original tape was made. The introduction of an encoder at the record cutter is said to improve the signal-to-noise ratio by as much as 30 decibels, resulting in enhanced dynamic range and quieter disc surfaces.

To play such a disc requires a special decoder added to one's stereo system. Its cost is $109. The encoder itself is not being offered by dbx to recording studios. Instead, dbx is using it to make its own records, which means of course that the company has entered the record field. Indeed, a list of the first 19 releases, mostly classical, has been issued. The new albums, cut from master tapes, carry prices of $8, $12 and $16, depending on original label osts to dbx. Among the labels represented are Vox, Orion, Desmar, Desto, Sine Qua Non, Chalfont and Varese Sarabande. There's also a dbx original "showcase" album.

First demonstrations of both the new Dolby and the new dbx systems proved duly impressive and both apparently work "as claimed." Of the two, the dbx made the greater impact on me since disc surface noise was dramatically reduced vis-a-vis the same record cut by conventional means. The Dolby effect on cassette tape was more subtle and would be of greater interest to serious recordists going after higher signal levels, particularly in the high frequencies.