Shares of Harman International Industries Inc fell as much as 10 percent on Tuesday after Apple Inc outlined plans to offer voice activated real-time traffic updates and turn-by-turn navigation in cars.
Harman, known for its audio devices, also makes car navigation products for luxury car makers such as Volkswagen AG's Audi and Daimler's Mercedes.
Shares in car navigation system maker Garmin Inc had also fallen in trading on Monday after Apple said it will enter the market by integrating its Siri voice application into car navigation systems.
Apple plans to make it easier for drivers to get directions by tapping a button on the steering wheel to launch Siri, a feature known as Eyes Free.
"Within the next 12 months, Siri will be the backbone for 'Eyes Free' service, integrating Siri and maps into automobiles," JPMorgan analyst Mark Moskowitz said.
Dutch vehicle navigation systems maker TomTom, however, is likely to benefit from Apple's move as it struck a deal to license its maps to the iPhone maker.
Apple is working with several automakers, including Audi, BMW AG, General Motors, Honda Motor Co, Mercedes and Toyota Motor Corp, to introduce the voice navigation system.
J.D. Power and Associates in January ranked Harman as the top supplier of factory-installed auto navigation systems.
Harman shares were down 9 percent on Tuesday on the New York Stock Exchange, adding to their 5 percent fall on Monday. Garmin shares, which fell 9 percent on Monday, were up 3 percent on the Nasdaq.
Navigation-technology provider TeleNav Inc's shares also fell as much as 12 percent and Robert W. Baird cut the stock to "underperform," saying Apple's new mobile mapping service may force the company to reduce prices.
(Reporting by Supantha Mukherjee in Bangalore; Editing by Anthony Kurian, Viraj Nair)