Improvements in Sound Technology

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Fig. 1

If you think there has not been much change in audio technology recently, then you missed the 2017 Consumer Electronics Show where a host of new technologies and products were on display. This is in addition to the plethora of Bluetooth earbuds that use wireless charging in addition to wireless connectivity.

One new technology was hidden in a corridor at Honda’s booth. VocalZoom was showing off its Human Machine Communications (HMC) sensor (Fig. 1). This high-precision microphone uses optics instead of sound vibrations through the air as with conventional audio microphones. The optical system implements an infrared range finder that detects skin vibration of a person speaking. This is most apparent around the throat, but much of the face provides sufficient feedback for the sensor.

The sensor does need to be aimed at the face, but this is easy with many application scenarios from tracking a car driver’s voice to someone using an automated teller machine (ATM). A head mounted approach could also be used. The advantage of this approach is that only the voice-related vibrations are recorded, so noise cancellation is not required. The sensor is not applicable to all voice command input applications, but the ability to essentially eliminate ambient noise from the input is hard to overlook.

Another key change in mobile audio is the use of USB Type-C connections instead of a headphone jack as with the latest Apple iPhone. Many have complained of the lack of a headphone jack, but the approach offers a range of advantages from a thinner device because of the Type-C connector to a digital audio interface. A USB audio device also provides better control and more information about the device to the operating system and applications using the device.

Fig. 2

Conexant’s tiny CX20988 (Fig. 2) is a low-cost Type-C audio CODEC that does not require a crystal, allowing it to fit into a very small package. It is available in a 3.09-mm2 WLCSP package. It delivers 24-bit stereo feedback with a 48 kHz sample rate and a five-band equalizer. It has a 1.5mA suspend current to minimize power requirements. It supports four-conductor headset jacks with auto-headset detection. It has multiple LED and button interfaces.

The slightly larger (5 mm2) CX20888 CODEC adds noise cancellation with features like a wake-on-voice trigger. It uses a 100 MHz, dual core, 32-bit DSP that utilizes a pair of PDM digital microphone interfaces (DMICs). 

Conexant also demonstrated an impressive smartphone application that works with the chip. It had the ability to disable noise cancellation and feed ambient sound into the headset so I could hear a person speaking to me without having to take off the earphones. It also provides significant listening and noise cancellations adjustment profiles.

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Discuss this Blog Entry 4

on Jan 27, 2017

The "vocal zoom" invention is very interesting, but it may still suffer in some very loud environments because of the speaker's face vibrating from the noise. But it will certainly enhance the snooping effectiveness for those so inclined, since at least in theory, all that would be needed to hear speech would be a telescope to see the speaker. So it will be very interesting to see how that part actually works.
The use of a USB-C connector instead of a standard audio connection is a great way to force folks to purchase the much more expensive headset instead of using the wide variety available on the market. A great profit invention but a good way to squeeze the customer. I would find it a deal-breaker, and shop for a different product, and I hope that others do the same. There is no other way to force this uninvited change to be rolled back.

on Jan 29, 2017

Actually the telescope may not work at least with this sensor. It is much akin to the Kinect sensor that has a limited range as well.

on Jan 27, 2017

The Soviets used a similar technology decades ago to spy on conversations by aiming electromagnetic radiation, either light or microwave RF at a closed window. The glass pane would act as a microphone diaphragm and the return radiation would be modulated by sound in the room.

on Jan 29, 2017

Actually this technology is commercially available and regularly used by police and security organizations. Likewise, there are defeating technologies that are also commercially available even on Amazon.

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William Wong

Bill Wong covers Digital, Embedded, Systems and Software topics at Electronic Design. He writes a number of columns, including Lab Bench and alt.embedded, plus Bill's Workbench hands-on column....
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