A small Silicon Valley company is suing Apple, alleging the computer maker infringed its patent covering noise-reduction technology for cell phones.

Noise Free Wireless said it presented its technology at several meetings at Apple's Cupertino, California, headquarters and provided it with detailed technical information prior to Apple filing its own patent for a similar technology. The technology has gone on to be used in the iPhone 4 and 4S and all three iPad models, it said.

The case centers on U.S. patent 7,742,790, which was filed by Noise Free in May 2007 and awarded to the company in June 2010. It covers a method for reducing or cancelling environmental noise, such as wind, from a voice transmission on a cell phone.

After filing its patent, Noise Free began approaching consumer electronics companies with details of its technology, according to its complaint. It first had contact with Apple in mid-2007 and presented its work to the company in September that year, it said.

Over the next three years the companies held a number of meetings at Apple's headquarters at which confidential material including an evaluation circuit board were made available, Noise Free said. The companies initially agreed verbally to confidentiality and then signed a formal non-disclosure agreement in September 2008.

The relationship between Apple and Noise Free went sour in August 2010 when Noise Free learned Apple had decided to use technology from a rival company, Audience, in its products.

In June that year, while the companies were still talking, Apple filed U.S. patent application 2011/0300806 covering a system for suppressing noise in a signal while retaining the user's voice.

Noise Free's complaint alleges Apple "extracted Noise Free's proprietary and confidential object code, determined Noise Free's noise reduction software and measured and duplicated the signal traces from the circuit board and microcontroller," and supplied the information to Audience.

Further, it says the Apple patent filing contains some of the ideas and inventions it disclosed to Apple.

Apple and Noise Free did not return calls for comment.

Noise Free Wireless, based in nearby Santa Clara, is asking the U.S. District Court for the Northern District of California to find Apple misappropriated trade secrets, breached contract, and engaged in unfair business practices. It wants damages for the alleged patent infringement and an invalidation of Apple's patent.

The case is number 12-03483, filed on July 3.

Martyn Williams covers mobile telecoms, Silicon Valley and general technology breaking news for The IDG News Service. Follow Martyn on Twitter at @martyn_williams. Martyn's e-mail address is martyn_williams@idg.com