OSAKA -- Matsushita Electric Industrial Co. and Honda Motor Co. have jointly realized a technological development to make car interiors quieter so that audio systems can be better heard, the two companies said Thursday.

The "active noise control" technology is especially effective when vehicles are traveling on rough terrain in the countryside or on ill-maintained roads, the firms said.

When an automobile, such as a sport utility vehicle, passes over a pothole or other road depression, the resultant shock tends to generate low-frequency noise that makes it difficult to hear music being played.

The sound control process involves first detecting road noises with a microphone attached under the driver's seat and then using a special speaker to emit acoustic waves to cancel out the sound.

As a result, listeners are better able to hear the low notes in music, the companies said.

Honda Motor will equip its restyled Accord station wagon, which goes on the market today, with the noise-control system, they said.

The new technology will also allow the automakers to build lighter vehicles as they will not need to add anti-noise devices to chassis, they said.

Experiments are being conducted on using the new method in ambulances to shield patients from siren wailings, they added.