Head-related transfer function measurement system
Head-related transfer function measurement system (Creating a 3D acoustic field using HRTF)
The head-related transfer function (HRTF) measurement system uses impulse response measurement technology and MT Series custom-designed microphone moving devices to measure numerous head-related transfer functions automatically and quickly.
Head-Related Transfer Function (HRTF) is defined as the transfer function from a central point between where the ears would be on a head-less subject, to the opening of the subject's ear canal or ear drum on a subject head in a free field. In simple terms, the HRTF describes how sound propagation is influenced by the shape of the human head and ears.
HRTF is known as a fundamental data of auditory directional perception and can be used for various purposes--from basic research to pseudo-surround audio systems and reproduction of a 3D sound field. People are surrounded by various sounds in their daily lives. For that reason, in order to reproduce a realistic space (stereophonic sound field) using sound technology, it is important to ensure that sounds "feel" as if they are coming from all directions (top, bottom, left, right, front, and back).
In recent years, systems capable of reproducing surround sound using only headphone or television speakers have been commercialized even in consumer products. In order to achieve such functionality, it is important to understand HRTF behaviors as basic data concerning human hearing perception.
HRTF measurement using a dummy head microphone
There are two ways to measure HRTF: using a dummy head microphone or performing actual measurement with a human as the subject. The dummy head microphone with a pair of built-in microphones in both ears imitates the geometry of an average human face and ears. However, we all hear sounds differently due to different shapes of heads, ears, and shoulders. As such, various kinds of dummy head microphones with different head and ear shapes are available. For this reason, we must keep in mind that we are using an average-shaped human face and ears when the goal is virtual reality.
HRTF also depends on directionality. For HRTF measurement in all directions, automated measurement using a microphone traverse system is effective.