Sound Reasons

A HAAC Microphone
A HAAC Microphone

When I bought my Lumia 620 I discovered that although it was a budget phone it had HAAC microphones and rich sound recording. I had absolutely no idea what that meant but it sounded good…

In this post I will discuss the audio technology of Lumia phones and why it is another sound reason to consider a Lumia phone.

The HAAC Microphone
Traditional microphones start distorting the sound when the level or amplitude becomes too loud. Nokia developed the patented HAAC (high amplitude audio capture) microphone. Basically there are two channels for the sound, one for regular sound levels, and one for very loud levels.

The software in the phone combines the channels intelligently. The result is that the phone is able to capture a very wide range of sound levels without distortion. (Links to a more technical description is given at the end of the post).

Rich Sound Recording
Sounds are captured and processed using 32bit software algorithms – that is high performance! This allows the software to improve the quality of the sound by providing wind noise reduction, microphone self-noise reduction, microphone equalizers (to fit product acoustics to frequency response requirements), camera autofocus noise reduction and automatic gain control.

On basic phones, like my Lumia 620, there are two microphones, one at the top and one at the bottom edge of the phone (or left and right edges when holding the phone horizontally).

When speaking on the phone, the lower microphone picks up your voice, while the top microphone captures ambient sound (mostly noise). The software uses the sound from the top mic to subtract the noise from your voice signal.

When capturing video, rich recording kicks in in a different way. Your phone is now held horizontally (or should be). The two microphones are now used to capture rich stereoscopic sound.

Once the sound from the two microphones have been cleaned up, they are combined with the information from the video camera into an mpeg container file (.mp4) and stored on your phone.

The diagram below shows the various components involved in rich sound recording.

blockdiagram

Multiple Microphones
HAAC microphones are inherently omnidirectional which means it picks up sound equally from all directions. When you are videotaping a performance or a person speaking at a podium, you would ideally want the microphones to be directional, i.e. recording what you are interested in, and ignoring all other sounds. This is illustrated in the diagram below:

directional recording

The more expensive Lumias (not my 620 I am afraid) have four microphones: two facing in the direction of the camera and two on the back. This allows the software algorithms to filter out the unwanted sounds from behind the person shooting the video, thus giving one excellent directional recording ability.

The Lumia 830, which is the phone I covet, has only one microphone at the back so the directional effect is not as perfect as on the 930 but it is still pretty good and gives excellent surround sound recordings for your videos. This I think is a reasonable compromise for an “affordable flagship” phone.

If you are technically inclined you can view these Nokia white papers.

In the next post I will discuss how to use the audio side of your phone in your business.