What is HPL?
- HPL stands for HeadPhone Listening.
- HPL is a binaural technology that is ideal for music production and listening
- HPL is one of the core technologies behind the 3DX and HPL2 Processor
- HPL is a technology developed and licensed by Acoustic Field Inc.
Why does HPL sound so good?
HPL uses a different method to that commonly used by general binaural plug-ins.
- General method: convolution of measured IR
- HPL: algorithmic room modeling and head acoustic simulation
The general convolution method uses Head-related Impulse Response data, which is measured by a dummy head placed in an anechoic room. This signal processing is similar to the convolution reverb often used in music production.
Sound processed in this way generally feels extremely close, as if it is being whispered in your ear. This creates a sense of “immersion”, which is important in the production of VR content.
However, there is a problem with this method when applied to music production. All sounds feel too close, and you lose the sense of spaciousness and distance that is so important in music production.
HPL was developed to achieve a sense of both “immersion” and “spaciousness”.
The following table shows the differences between the general method and HPL.
|Localization||Out-of-head localization||Very close to the surface of the head|
|Perception of space||Natural||Needs additional processing. It is difficult to avoid unwanted side-effect and unnatural result.|
|Uniformity of panning||Equal volume in all direction||louder in the left/right position, softer in the front/back and up/down positions|
Is HPL an application of Ambisonic technology?
No. HPL does not use Ambisonic technology in any way.
Many binaural plug-ins process the signal once it has been encoded into Ambisonics. However, NovoNotes plug-ins binauralize the virtual speakers without encoding them to ambisonics. This provides a higher localization. We use this method because, in music production, we cannot afford to compromise on either immersion or localization.
When the 3DX input is set to ambisonics, the HPL processor binaurally converts the signal once it has been decoded to virtual speakers.