Toyota's Prius hybrid is becoming a little less quiet with a new electronic humming device the automaker hopes answers complaints from pedestrians who can't hear the top-selling car approaching.

The ¥12,600 speaker system, which will be installed under the hood of the third-generation Prius, sets off a whirring sound designed to be about the same noise level as a regular car engine so it isn't annoying, Toyota Motor Corp. said Tuesday.

It goes on sale Aug. 30 in Japan, and owners pay extra for installation charges. Its use is voluntary.

Overseas sales plans are still undecided, but Toyota is studying regulations and considering offering it in the U.S. and other markets, spokeswoman Monika Saito said.

The gasoline-electric hybrid gets good mileage but is also quiet because it runs as an electric motor much of the time. That advantage has drawn complaints that pedestrians, the blind in particular, are at greater risk of being hit by the car, especially at low speeds.

The U.S. government's auto safety agency found in a research report last year that hybrids are twice as likely to be involved in accidents involving pedestrians at low speeds compared with cars with conventional engines.

Toyota said it plans versions of the device for other hybrid models, plug-ins, electric vehicles and fuel-cell vehicles.

Pedestrian deaths compared with overall traffic fatalities are higher in Japan than in the U.S. and many other nations because of Japan's narrow and crisscrossing crowded streets. Japan is also a rapidly aging society, making audible cars critical.

Toyota said the device is based on guidelines addressing the dangers of silent cars, including hybrids, issued in January by the government.