The popularity of Apple’s iPhone 6S and other products is boosting the microelectromechanical-systems (MEMS) microphones market to a compound annual growth rate (CAGR) of 11 percent from 2015 to 2019. The market is forecast to reach 5.8 billion units, with $1.3 billion in revenue, in 2019. Apple, which shifted from three MEMS microphones in the iPhone 6 line to four in the iPhone 6S line, will purchase more than one billion MEMS microphones in 2016 for the iPhone, according to IHS Inc. (NYSE: IHS).

“Prior to Apple, Microsoft and Motorola had already introduced some smartphones with four MEMS microphones, but in lower volumes,” said Marwan Boustany, senior analyst for MEMS and Sensors for IHS Technology. “Following Apple’s lead, additional manufacturers are expected to start including between two and four MEMS microphones in mobile handsets.”

Apple is expected to purchase more MEMS microphones than Samsung Electronics, Xiaomi and Huawei combined in 2016. When counting the MEMS microphones used for the iPad, and for the earbuds sold with Apple’s iPhone, Apple Watch and Macbook notebooks, Apple accounted for a third of the total consumption of MEMS microphones in 2015.

The move to three or four microphones is currently driven by hands-free calling and voice commands for Siri, Google Now, Cortana and other apps, which are becoming an increasingly important means of interaction between consumers and their smartphones. Additional MEMS microphones are also added on the back of the phone for richer audio fidelity in video recording, noise cancellation and better call and recording performance.

“It will be harder for manufacturers to justify a move to five microphones in the coming years, unless clear and potentially popular use cases are identified,” Boustany said. “So far, Motorola’s Droid Turbo is the only handset with five MEMS microphones to become widely available.”

Knowles remains the market leader in MEMS microphone shipments and revenue, but the company’s share is eroding. Goertek, STMicroelectronics and AAC have recently made great gains in the market, selling to Apple and other companies, according to the IHS MEMS & Sensors for Consumer and Mobile Intelligence Service.