IMOS - ANMN Passive Acoustic Observatory at Portland, VIC (PAPOR)

The Portland Passive Acoustic Observatory consists of two to four moorings fitted with hydrophones set on the seabed at ~170 m depth that record noise in the ocean. This system can be used to monitor whale and fish migrations, seismic activity and other natural and man-made noise sources. If four moorings are set they are configured with a mooring at each apex of an approximate equilateral triangle of 5 km side with the fourth mooring in the triangle centre. Temperature loggers are set on each mooring at the seabed.\n\nEach logger records at a sampling rate of 6 kHz for between 3-8 min of every 15 min. If four loggers are set a 22 kHz recording is also made once a day to allow accurate synchronisation of the instrument clocks. This is required for locating the source of a sound based on its time of arrival at each hydrophone in the array. A 7 kHz pinger set on the central mooring pings for 35 minutes at a 20 s interval once per day to overlap the 22 kHz sample.\n\nRaw data from each logger is in the form of mixed binary/text files comprised of:\n1) text header and footer containing recording start and end date/time, quality control and sampling configuration; and\n2) sea noise data of 16 bit unsigned integer, binary values (IEEE, little endian).\n\nInstruments are calibrated for system gain with white noise of known level input with the hydrophone in series, before and after deployments. System calibrations are made over 2 Hz to the Nyquist frequency. The instrument clock drift is checked against GPS transmitted UTC time before and after deployment.\n\nThe raw data can be obtained on portable disk from IMOS eMarine Information Infrastructure (eMII).\n\nThe Centre for Marine Science and Technology (CMST) at Curtin University has developed Matlab software to process and analyse these data.

波特兰被动声学观测站（Portland Passive Acoustic Observatory）由2至4套锚系系统组成，每套锚系搭载水听器（hydrophone）布设于约170米深的海底，用于记录海洋环境噪声。该系统可用于监测鲸类与鱼类洄游、地震活动，以及其他自然与人为噪声源。当布设4套锚系时，它们将以边长5公里的近似等边三角形的三个顶点各部署一套，第四套锚系布设于三角形中心。每套锚系的海底位置均搭载温度记录仪。

每台记录仪的采样频率为6千赫兹，每15分钟内记录3至8分钟的数据。若部署4台记录仪，则每日额外开展一次22千赫兹的采样，以实现各仪器时钟的精准同步——这是基于声波到达各阵元水听器的时间差来定位声源的必要前提。布设于中心锚系的7千赫兹声信标，每日以20秒的间隔持续发射声脉冲35分钟，以与22千赫兹采样时段实现重叠。

各记录仪的原始数据为二进制与文本混合文件，包含两部分：1）文本形式的头文件与尾文件，其中包含记录的起止日期与时间、质量控制信息与采样配置参数；2）16位无符号整数格式的海洋噪声二进制数据（遵循IEEE标准，采用小端序存储）。

在每次部署前后，均会通过串联水听器输入已知幅值的白噪声，对系统增益进行校准。系统校准的覆盖频段为2赫兹至奈奎斯特频率（Nyquist frequency）。在部署前后，还会对照GPS发射的UTC时间对仪器时钟漂移进行校正。

原始数据可通过IMOS海洋电子信息基础设施（eMarine Information Infrastructure, eMII）提供的便携式磁盘获取。

科廷大学（Curtin University）海洋科学与技术中心（Centre for Marine Science and Technology, CMST）已开发用于处理与分析此类数据的Matlab软件。