ABSTRACT

We have developed a method of animal localisation that detects the angle from a sensor towards the direction of an animal call. The method is as simple to use as deploying a conventional static sound recorder, but provides tracking information as well as sound recordings. The principal of operation is to detect the phase difference between microphones positioned closely together. The phase is detected by converting the signals to their analytic form with a Hilbert transform. The angle is then calculated from the phase difference, frequency and microphone separation. Angular measurements provide an indication of flight paths above the sensor, and can give details of activity and behaviour that are not possible with a single channel static recorder. We recorded flight paths for 5 bat species at a site in Denmark (Pipistrellus nathusii, Pipistrellus pygmaeus, Eptesicus serotinus, Myotis daubentonii and Nyctalus noctula). The median error in angular measurement for the species was between 3 and 7 degrees. Calls at high angles from normal, corresponding with a poor sensor sensitivity, had larger errors compared to calls recorded in the centre of the field of view. Locations in space could be estimated by combining angular measurements from two or more sensors.

摘要

我们开发了一种动物定位方法，可以检测从传感器到动物叫声方向的角度。该方法与部署传统静态录音机一样简单，但提供跟踪信息和录音。工作原理是检测靠近放置的麦克风之间的相位差。通过使用希尔伯特变换将信号转换为其解析形式来检测相位。然后根据相位差、频率和麦克风间隔计算角度。角度测量提供了传感器上方飞行路径的指示，并且可以提供单通道静态记录器无法提供的活动和行为的详细信息。我们在丹麦的一个地点记录了 5 种蝙蝠的飞行路径（Pipistrellus nathusii、Pipistrellus pygmaeus、Eptesicus serotinus、Myotis daubentonii和Nyctalus noctula )。该物种角度测量的中值误差在 3 到 7 度之间。与在视野中心记录的呼叫相比，与法线高角度的呼叫与较差的传感器灵敏度相对应，具有更大的误差。空间中的位置可以通过结合来自两个或多个传感器的角度测量来估计。