VR系列——Oculus Audio sdk文档：一、虚拟现实音频技术简介（6）——空间化的音响设计

声音的空间化主要采用单声道技术，而避免正弦波等只能提供很少频率的纯音，应采用广谱源的多频率，以避免HRTF不能有效的过滤频率内容，以及不能有效的掩盖人为加工的可听得见的声音差错，造成空间效果不理想，同时确保高于1500HZ的频率内容，帮助定位声音的方向。

音频格式同样需要考虑会不会增加成本，同时造成延迟，最好如目标设备的输出格式保持一致。

现在，我们已经确定了声音在世界上是如何产生的，更重要的是，我们如何诱导人们认为声音是从空间中一个特定的点传来的，我们需要考虑如何改变声音设计的方法，让其支持空间化。

Now that we've established how humans place sounds in the world and, more importantly, how we can fool people into thinking that a sound is coming from a particular point in space, we need
to examine how we must change our approach to sound design to support spatialization.

单声道（Mono）

大多数的空间定位技术模型的声源为无限小的点源；即，在空间中，声音的处理是从单个的点源进行处理的，而不是对一个大面积，或一对离散扬声器进行处理的。
Most spatialization techniques model sound sources as infinitely small point sources;
that is, sound is treated as if it were coming from a single point in space as opposed to a large area, or a pair of discrete speakers. As a result, sounds should be authored
as monophonic (single channel) sources.

避免正弦波（Avoid Sine Waves）

如正弦波等道缺乏谐音或泛音的纯音，存在着一些问题：

Pure tones such as sine waves lack harmonics or overtones, which presents several issues:

在现实世界中，纯粹的音调通常不会发生，所以它们通常听起来很不自然。这并不意味着你可以完全避免纯音的出现，因为许多VR体验是抽象的，但也是有价值的。
HRTF的作用是过滤频率的内容，由于纯音缺乏这样的内容，通过的HRTF滤波频率进行工作时，很难使其空间化。
在HRTF过程中任何差错或间断都会更容易听得出来，因为没有额外的频率内容来掩盖人为加工。一种移动的正弦波往往会给空间化带来最严重后果。

Pure tones do not commonly occur in the real world, so they often sound unnatural. This does not mean you should avoid them entirely, since many
VR experiences are abstract, but it is worth keeping in mind.
HRTFs work by filtering frequency content, and since pure tones lack that content, they are difficult to spatialize with HRTFs.
Any glitches or discontinuities in the HRTF process will be more audible since there is no additional frequency content to mask the artifacts. A
moving sine wave will often bring out the worst in a spatialization implementation.

使用广谱源（Use Wide Spectrum Sources）

与纯音调难以空间化的原因一样，广谱的声音为HRTF提供多频率，因此空间化的效果较好。同时也帮助掩盖由于HRTFs、筛选、衰减的动态变化而引起的可听得见的差错。除了广谱的频率外，还确保有显著的高于1500Hz的频率内容，因为这被人类大量地用来做声音定位。
For the same reasons that pure tones are poor for spatialization, broad spectrum sounds work well by providing lots of
frequencies for the HRTF to work with. They also help mask audible glitches that result from dynamic changes to HRTFs, pan, and attenuation. In addition to a broad spectrum of frequencies,
ensure that there is significant frequency content above 1500 Hz, since this is used heavily by humans for sound localization.

低频的声音对人类来说是难以定位的–这就是家庭影院使用单声道重低音声道的原因。如果一个声音主要是低频（隆隆声、嗡嗡声、抖动等），那么你可以避免空间化的上限，使用筛选/衰减来替代。
Low frequency sounds are difficult for humans to locate - this is why home theater systems use a monophonic subwoofer channel. If a sound is predominantly
low frequency (rumbles, drones, shakes, et cetera), then you can avoid the overhead of spatialization and use pan/attenuation instead.

避免实时格式转换（Avoid Real-time Format Conversions）

从一种音频格式转换为另一种，可能需要较大的代价，而且会引入延迟。所以声音应该以目标设备的相同输出格式（采样率和比特深度）来输出。对于多数的PC机来说，输出格式应该是16bit、44.1kHz PCM，但是有些平台可能有不一样的输出格式（如在Gear VR 上，是16bit、48kHz）。

Converting from one audio format to another can be costly and introduce latency, so sounds should be delivered in the same output format (sampling rate
and bit depth) as the target device. For most PCs, this will be 16-bit, 44.1 kHz PCM, but some platforms may have different output formats (e.g. 16-bit, 48 kHz on Gear VR).

空间化的声音是单声道的，因此应该被编为单声道，以避免在运行时的立体声合并（将引入相位和体积伪影）。

Spatialized sounds are monophonic and should thus be authored as a single channel to avoid stereo-to-mono merging at run-time (which can introduce phase
and volume artifacts).

如果你使用非本地格式的音频，考虑在安装或加载的时候转换为本地格式，以避免运行时冲突。

If your title ships with non-native format audio assets, consider converting to native format at installation or load time to avoid a hit at run-time.