VR系列——Oculus Audio sdk文档：一、虚拟现实音频技术简介（4）——听觉设备

使用扬声器阵列会造成VR难以捕获头部和用户的运动，而头戴式耳机能带来更好的沉浸式，头部运动更容易捕获，HRTF同样可以更精确，回声影响也相对较小，特别是便于携带，将成为VR的主流标配。

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传统地，高品质的音频再现已经成为多扬声器系统的领域，常常带有一个或者多个的低音炮。然而，随着网络游戏和语言聊天的兴起，很多玩家都转换到耳麦上（耳机与麦克风的集合体）。

Traditionally, high quality audio reproduction has been the domain of multi-speaker systems, often accompanied by one or more subwoofers. However, with the rise of online gaming and voice chat, many players have transitioned to headsets (headphones with integrated microphones).

对于当前的VR，特别是需要追踪头部和用户的运动，扬声器阵列已经是一个进化的死胡同。头戴式耳机将是VR的标配，因为它提供了更好的独立性、隐私性、便携性和空间性。

For modern VR, especially with head tracking and user movement, speaker arrays are an evolutionary dead end. Headphone audio will be the standard for VR into the future, as it provides better isolation, privacy, portability, and spatialization.

头戴式耳机（Headphones）

与自由声场话筒系统（free-field speaker systems）相比，在VR音频领域，头戴式耳机有以下几个优点：

Headphones offer several significant advantages over free-field speaker systems for virtual reality audio:

• 听觉与听者所在环境的增强现实与沉浸式相独立。
• 头部的追踪变得很简单。
• HRTF变得更准确，因为不会受到其他HRTF的修改以及自己身体的影响。
• 听众更容易控制HMD设备。
• 耳机放置地很理想，不会受到回声的影响。

• Acoustic isolationfrom the listener's environment enhance realism and immersion.
• Head trackingis greatly simplified.
• HRTFsare more accurate since they don't suffer from the “doubling down” of HRTF effects (sounds modified from the simulated HRTF, and again by the listener's actual body geometry).
• Access to controlswhile wearing an HMD is far simpler when those controls are physically attached to the listener.
• Microphonesare ideally placed and subject to much less echo/feedback.

当前的耳机种类有以下几种，各自有优点和缺点：

Headphones are available in a variety of types with various trade-offs:

关闭式耳机（Closed Back Headphones）

一般来说，这种型号的耳机可以提供最好的隔离以及音响效果。然而，封闭式结构可能会导致不舒服（由于热量和重量），由于内共振，他们倾向于提供较少的音频再现。而且，如果强加或高于耳朵时，会压紧耳廓引起轻微的音频再现。

As a general rule of thumb, closed back headphones offer the most isolation and bass response. However, the closed construction may lead to discomfort (due to heat and weight), and they tend to offer less accurate reproduction due to internal resonance. Also, if placed on or over the ear, they cause the pinnae to impact sound reproduction slightly.

听觉的隔离可以提升沉浸的效果，让听者与外界环境隔绝，听不到有人走进屋子、手机响、门铃响等。这是不是一件好事，因人而异。

While acoustic isolation can help with immersion, it cuts listeners off from their environment so they may be unable to hear others entering the room, cell phone ringing, doorbell, et cetera. Whether that is a good thing or not is up to the individual.

开放式耳机（Open Back Headphones）

开放式耳机通常比封闭式耳机更加精准和舒适，除了他们并不使听者隔绝于外部环境，并将声音播放到周围环境中外。这可以通过低音炮进行配合，这样很合适作为VR中安静的区域的一种体验。

Open back headphones are generally more accurate and comfortable than closed-back headphones, but they do not isolate listeners from the exterior environment, and broadcast to the surrounding environment as well. These are suitable for quiet areas devoted to a VR experience, possibly in conjunction with a subwoofer.

正如封闭式耳机一样，当将其放在耳边或罩在耳朵上时，开放式耳机允许发出耳机中语音片轻微的撞击声。

As with closed back headphones, when placed on or over the ear, open back headphones allow the pinnae to impact sound reproduction slightly

耳内式（Earbuds）

耳机（如用于手机或便携式音乐播放器）价格便宜、重量轻、非常轻便，虽然他们通常缺乏低音。一些型号，如苹果的EarPods，他的频路响应非常好，虽然有一个稳定的低音频率，这些在空间化大多是被忽略的。

Earbuds (such as those that ship with cell phones or portable music players) are cheap, lightweight, and very portable, though they typically lack bass. Some models, such as Apple EarPods, have surprisingly good frequency response, albeit with a steady roll off of bass frequencies. These are mostly ignored for spatialization.

大多数的耳机隔音效果不好。

Most earbuds are poor at isolation.

入耳式监听器（In-Ear Monitors）

入耳式监听器提供了优越的环境隔离效果，是非常轻量级的，并且在整个范围内都具有极好的频路响应。他们从听者的耳廓处消除声音的影响（不像头戴贴耳式耳机）。他们必须插入耳道，进而完全消除从耳道中传入声音的影响（因为大多数HRTFs（头部相关传输函数）捕获的正是外耳道的声音）。

In-ear monitors offer superior isolation from your environment, are very lightweight, and have excellent frequency response over the entire range. They remove the effects of the listener's pinnae from sound (unlike on-ear headphones). They have the downside of requiring insertion into the ear canal, which eliminates the effects of the ear canal from sound reproduction entirely (since most HRTFs are captured with microphones right outside the ear canal).

脉冲响应（Impulse Responses）

像所有的传感器一样，耳机通过自身独特的信号进行传输，同时通过HRTFs对频率的敏感性，将耳机字符从信号中去除对信号传输更有利。他可以通过对等的输出信号与耳机的脉冲响应来完成。

Headphones, like all transducers, impart their own characteristics on signals, and since HRTFs are frequency sensitive, removing the headphone character from the signal will usually be beneficial. This can be accomplished by deconvolving the output signal with the headphone's impulse response.

外部扬声器系统（External Speaker Systems）

直到最近，提供声音沉浸感最常见的方式是将扬声器环绕在听者周围，如杜比5.1或7.1声道的配置。然而部分音响具有固定的、狭窄的设置位置，故扬声器阵列系统遭受关键缺陷的困扰：

Until recently, the most common way to provide sound immersion was to surround the listener with speakers, such as a Dolby 5.1 or 7.1 speaker configuration. While partially effective for a fixed and narrow sitting position, speaker array systems suffer from key drawbacks:

• 在听力区域大部分移动镜头造成非精确成像。
• 没有音源仰角的线索，声音只是360度的出现在听众周围
• 只能假设听众固定不动，尤其是没有头部跟踪技术
• 如混响和反射的空间效果影响回声
• 较差的隔离效果意味着外界的声音会干扰VR的体验

• Imprecise imagingdue to panning over large portions of the listening area.
• No elevation cues, sounds only appear in a 360 degree circle around the listener.
• Assumption ofimmobile listener; in particular, no head tracking.
• Room effects such as reverberation and reflections impact the reproduced sound.
• Poor isolationmeans that outside sounds can intrude on the VR experience.

多扬声器配置将是常见的或有效的家庭VR应用程序，这是令人质疑的，但是，他们可能是可行的专用的商业设施。

It is doubtful that multi-speaker configurations will be common or effective for home VR applications, though they may be viable for dedicated commercial installations.

蓝牙（Bluetooth）

蓝牙已经成为一种流行的无线音频广播的通信方式。不幸的是，现代的蓝牙实现往往带来了相当大的延迟,有时高达500毫秒。因此，蓝牙技术不建议用于音频输出。

Bluetooth has become a popular communication method of wireless audio broadcast. Unfortunately, modern Bluetooth implementations often incur significant latency, sometimes as high as 500 milliseconds. As a result, Bluetooth technology is not recommended for audio output.