声音可以看见东西吗？
大家还记得多普勒效应吗？当声源与观察者发生相对运动时，观察者接收到的声音的频率会发生变化。最近，微软研究院的的研究人员利用多普勒效应开发了识别软件SoundWave来识别人体姿势。姿势识别已经不是新鲜的话题，微软的Kinect用摄像头实现了姿势识别。但是利用声音识别姿势的最大的好处是只需扬声器与麦克风就可实现，而这两者几乎是所有笔记本上都有的。
具体做法是：扬声器不断发出20-22KHZ的超声波，如果电脑周围没有物体移动，麦克风接受到的声音频率保持不变，如果物体靠近电脑，麦克风接收到的声音频率变高，物体远离，接收到的频率变低。这种现象发生的方式是可以预测的，通过分析频率可以确定移动物体的大小，物体移动的速度与方向，从而可以推理出人体姿势。
目前SoundWave的识别率达到了90%，而且在用户摆出姿势与电脑的识别反应之间没有明显的延迟。软件可以识别出的姿势包括“手的移动，手臂的弯曲，以及身体与电脑的相对移动。可以利用这些识别出的姿势控制电脑实现交互。比如利用手势来控制网页内容的滑动或者页面之间跳转，人体与电脑的相对移动则可以将电脑睡眠或唤醒。虽然SoundWave能识别的姿势有限，但是对于用户交互交互来说已经足够，特别是用户要记住这些姿势来完成交互。
SoundWave的另一优点就是不受光照的影响，这是传统视觉识别的一大弊端。其实在你的周围有很多感应器，只是你在与他们交互的过程中没有意识到他们的存在。
Ref: http://www.technologyreview.com/web/40368/?mod=chfeatured
ACM CHI上的文章：SoundWave: Using the Doppler Effect to Sense Gestures
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