Virtual cardioid microphone
By using the spatial property conveyed in SOPA (Stream Of Panoramic Audio) data, directionality of the sound can be controlled programmatically. It is a sort of "virtual cardioid microphone."
Since the spatial property of the sound at the observation point can be measured by a miniature head simulator, a microphone with any disired polar pattern can be created programmatically.
By activating the virtual cardioid microphone, sensitivity to sound from one direction can be made higher than that of sound from other directions.
When using a real (not virtual) cardioid microphone, you can control the aiming direction only during the recording. Once the recording is made, you cannot change the aiming direction afterwards.
In the virtual cardioid microphone, directionality is created programmatically
during the reproduction. You can, therefore, change the target direction
whenever you like while you are listening to the sound.
In the following demo, a virtual cardioid microphone can be activated so that you can make sounds from the particular direction pop out and those from other directions suppressed.
By clicking one of the thumbnails above, you can start the demo.
On the demo screen, a panoramic image will be displayed under which, you will see a button.
Once the image is loaded and the instruction saying 'Click to start' or 'Tap to start' appears, you can start playing sound by clicking (tapping) on the image.
While the SOPA file is being played, you can switch the directionality modes by clicking (tapping) the button below the image.
There are 3 modes, that are 'Omnidirectional,' 'Cardioid' and 'Narrow.'
When 'Cardioid,' or 'Narrow' directionality is selected, the sounds from the front direction are enhanced (sounds from the rear direction are suppressed).
The figure below shows polar patterns of the 'Ominidirectional,' 'Cardioid'
and 'Narrow' directionalities.
Fig. Polar patterns of virtual cardioid microphone
You can control the target direction by panning the image. If you are using a mobile device, panning can be controlled by the rotary motion of the device.