By this demo, you can use your iPhone to roughly measure the DB around, while the view will change up&down with the value, to make it more intuitive. Clutter and noise can't be avoided, and the filter is needed, so a simple average filter is written here. 通过这个demo, 你可以用你的iPhone手机粗略地测量周围的分贝数, 与此同时, 视图会随着数值的高低而改变高度, 来使其更直观. 杂波和噪音是无法避免的, 需要滤波处理, 这里写了一个简单的均值滤波器.