Recordings of underwater sound and detections of marine mammals from sonobuoys deployed during 2019 ENRICH Voyage (IN2019_V01)

This dataset contains acoustic recordings from Directional Frequency Analysis and Recording (DIFAR) sonobuoys that were deployed from 19 January – 5 March 2019 during the ENRICH (Euphausiids and Nutrient Recycling in Cetacean Hotspots) voyage (IN2019_V01). 295 sonobuoys were deployed yielding 828 hours of acoustic recordings. Passive acoustic research during ENRICH took the form of both broad-scale structured surveys and fine-scale adaptive surveys depending on the operational mode of the ship. Regardless of the mode of operation, listening stations were conducted by deploying SSQ955 sonobuoys (commonly called HIDAR sonobuoys) in Directional and Frequency Analysis and Recording (DIFAR) mode to monitor for and measure bearings to vocalising whales while the ship was underway (Miller et al. 2015). During transit, listening stations were conducted every 30 nmi in water depths greater than 200 m when Beaufort sea state was less than 7. During marine science stations, sonobuoys were deployed approximately 2-4 nmi prior to stopping in order to attempt to monitor them for the full six-eight hour duration of their operational life or the duration of the station. The sampling regime was chosen for compatibility with previous surveys, and to balance spatial resolution with the finite number of sonobuoys available for this study. During portions of the voyage dedicated to passive acoustic tracking, multiple sonobuoys were deployed concurrently to precisely locate Antarctic blue whales (Miller et al. 2015, 2016). Bearings from single sonobuoys, pairs, or triplets were also followed in order to track, locate, and sight blue whales to obtain visual observations of group size, behavior, and photographic identifications. Tracking was conducted during 10 days spread throughout the voyage: 30 Jan, and 2, 5, 9, 13, 17, 19, 22-24 Feb 2019 for a total of 124.1 hours. When conducting activities with whales, sonobuoys were deployed adaptively, often in pairs or triplets with 6-9 nmi spacing. When possible during acoustic tracking, the acousticians also continued to monitor other groups of whales that were judged to be nearby (e.g. within a 20-30 nmi radius of the array), as well as more distant animals. Triplets of sonobuoys were also occasionally deployed during small-scale active acoustic surveys even if there was no opportunity to approach whales.Instrumentation, software, and data collectionAt each listening station, a sonobuoy was deployed with the hydrophone set to a depth near 140 m. Sonobuoys transmitted underwater acoustic signals from the hydrophone and directional sensors back to the ship via a VHF radio transmitter. Radio signals from the sonobuoy were received using an omnidirectional VHF antenna (PCTel Inc. MFB1443; 3 dB gain tuned to 144 MHz centre frequency) and a Yagi antenna (Broadband Propagation Pty Ltd, Sydney Australia) mounted on the aft handrail of the flying bridge. The antennas were each connected to a WiNRADiO G39WSBe sonobuoy receiver via low-loss LMR400 coaxial cable.The radio reception range on the Yagi antenna was similar to previous Antarctic voyages, and was adequate for monitoring and localisation typically out to a range of 10-12 nmi, provided that the direction to the sonobuoy was close (i.e. within around 30o) to the main axis of the antenna. The radio reception on the omnidirectional antenna typically provided 5-10 nmi of omnidirectional reception from sonobuoys. At transit speed (8-11 knots), the Yagi antenna provided about 75 minutes of acoustic recording time per sonobuoy. Using both antennas together were able obtain radio reception for up to six hours (i.e. the maximum life of a 955 sonobuoy) when sonobuoys were deployed within 5 nmi of a marine science station.Received signals were digitised via the instrument inputs of a Fireface UFX sound board (RME Fireface; RME Inc.). Digitised signals were recorded on a personal computer as 48 kHz 24-bit WAV audio files using the software program PAMGuard (Gillespie et al. 2008). Data from both the Yagi and Omnidirectional antennas were recorded simultaneously as WAV audio channels 0 (left) and 1 (right) and 2. Each recorded WAV file therefore contains a substantial amount of duplication since both antennas and receivers were usually receiving the same signals from the same sonobuoy.Directional calibrationThe magnetic compass in each sonobuoy was not calibrated/validated upon deployment because the ship did not generate enough noise.Intensity calibrationIntensity calibration and values followed those described in Rankin et al (2019).Sonobuoy deployment metadataThe PAMGuard DIFAR Module (Miller et al. 2016) was used to record the sonobuoy deployment metadata such as location, sonobuoy deployment number, and audio channel in the HydrophoneStreamers table of the PAMGuard database (In2019_V01.sqlite3). A written sonobuoy deployment log (SonobuoyLog.pdf) was also kept during the voyage, and this includes additional notes and additional information not included in the PAMGuard Database such as sonobuoy type, and sonobuoy end-time.Real-time monitoring and analysis:Aural and visual monitoring of audio and spectrograms from each sonobuoy was conducted using PAMGuard for at least 5 minutes after deployment only to validate that the sonobuoy was working correctly.Additional information about sonobuoys is contained in the file: Sonobuoy data collection during the TEMPO voyage - 2021-01-15.pdfReferencesGreene, C.R.J. et al., 2004. Directional frequency and recording ( DIFAR ) sensors in seafloor recorders to locate calling bowhead whales during their fall migration. Journal of the Acoustical Society of America, 116(2), pp.799–813.Miller, B.S. et al., 2016. Software for real-time localization of baleen whale calls using directional sonobuoys: A case study on Antarctic blue whales. The Journal of the Acoustical Society of America, 139(3), p.EL83-EL89. Available at: http://scitation.aip.org/content/asa/journal/jasa/139/3/10.1121/1.4943627.Miller, B.S. et al., 2015. Validating the reliability of passive acoustic localisation: a novel method for encountering rare and remote Antarctic blue whales. Endangered Species Research, 26(3), pp.257–269. Available at: http://www.int-res.com/abstracts/esr/v26/n3/p257-269/.Rankin, S., Miller, B., Crance, J., Sakai, T., and Keating, J. L. (2019). “Sonobuoy Acoustic Data Collection during Cetacean Surveys,” NOAA Tech. Memo. NMFS, SWFSC614, 1–36.

本数据集包含2019年1月19日至3月5日期间，在ENRICH（鲸类热点区域的磷虾与营养循环，Euphausiids and Nutrient Recycling in Cetacean Hotspots）航次（航次编号IN2019_V01）中部署的定向频率分析与记录（Directional Frequency Analysis and Recording, DIFAR）声呐浮标（sonobuoy）的声学录音。本次航次共部署295个声呐浮标，累计获得828小时的声学录音数据。

ENRICH航次的被动声学研究根据船舶作业模式，分为大尺度结构化调查与小尺度自适应调查两种形式。无论采用何种作业模式，船舶在航行过程中均会部署SSQ955型声呐浮标（通常称为HIDAR声呐浮标），并将其设置为定向频率分析与记录（DIFAR）模式，以监测并定位发声鲸类的方位（Miller等，2015）。

在航行过境阶段，当蒲福海况（Beaufort sea state）低于7级且水深超过200米时，船舶每航行30海里（nautical mile, nmi）即布设一处监听站位。在海洋科学考察站位作业前约2-4海里处即部署声呐浮标，以便在其6-8小时的全工作时长内，或整个考察站位作业时段内完成监测。本次采样方案的选取既兼容既往调查标准，也兼顾了空间分辨率与本研究可用声呐浮标的有限数量。

在航次中专门用于被动声学追踪的时段内，研究人员会同时部署多个声呐浮标，以精准定位南极蓝鲸（Miller等，2015, 2016）。通过单个、成对或成组三个声呐浮标获取的方位数据，可追踪、定位并目视观测蓝鲸，记录其种群规模、行为模式并进行照片识别。声学追踪作业共开展10天，分别为2019年1月30日以及2月2日、5日、9日、13日、17日、19日、22日至24日，累计时长124.1小时。在开展鲸类相关研究活动时，声呐浮标会以自适应方式布设，通常以成对或成组三个的形式部署，浮标间距为6-9海里。在声学追踪作业期间，若条件允许，声学研究人员还会持续监测阵列周边20-30海里范围内的其他鲸类群体，以及距离更远的个体。即使暂时没有机会靠近鲸类，在小尺度主动声学调查中也会偶尔布设成组三个的声呐浮标。

## 仪器、软件与数据采集
在每一处监听站位，声呐浮标的水听器（hydrophone）均布设于接近140米的深度。声呐浮标通过甚高频（Very High Frequency, VHF）无线电发射机，将水听器与定向传感器采集的水下声学信号回传至母船。研究人员采用全向VHF天线（PCTel Inc. MFB1443，中心频率调谐至144 MHz，增益3 dB）与安装在飞行甲板后扶手处的八木天线（Broadband Propagation Pty Ltd，澳大利亚悉尼）接收声呐浮标的无线电信号。两根天线均通过低损耗LMR400同轴电缆连接至WiNRADiO G39WSBe型声呐浮标接收机。

八木天线的无线电接收范围与既往南极航次相当，当声呐浮标的方位接近天线主轴线（约30°范围内）时，其监测与定位范围通常可达10-12海里，可满足作业需求。全向天线的接收范围通常为5-10海里，可实现全向覆盖。在8-11节的航行速度下，八木天线单浮标的声学录音时长约为75分钟。若声呐浮标部署在海洋科学考察站位5海里范围内，同时使用两根天线可实现最长6小时的无线电信号接收，即SSQ955型声呐浮标的最大工作时长。

接收信号通过Fireface UFX声卡（RME Fireface；RME Inc.）的仪器输入接口完成数字化。数字化信号经PAMGuard软件（Gillespie等，2008）录制为48 kHz、24位的WAV格式音频文件。八木天线与全向天线采集的数据会同时作为WAV音频的0（左）、1（右）及2声道存储。由于两根天线与接收机通常会接收到来自同一声呐浮标的相同信号，因此每个录制的WAV文件均包含大量重复数据。

## 定向校准
由于母船噪声过大，每个声呐浮标的磁罗盘在部署时未进行校准或有效性验证。

## 强度校准
强度校准方法与参数均遵循Rankin等（2019）的描述。

## 声呐浮标部署元数据
研究人员使用PAMGuard DIFAR模块（Miller等，2016）记录声呐浮标部署元数据，包括位置、浮标部署编号及音频声道等信息，存储于PAMGuard数据库（In2019_V01.sqlite3）的HydrophoneStreamers表中。航次期间同时留存了书面声呐浮标部署日志（SonobuoyLog.pdf），其中包含PAMGuard数据库未收录的额外信息，例如声呐浮标类型与浮标终止工作时间。

## 实时监测与分析
在声呐浮标部署后的至少5分钟内，研究人员通过PAMGuard对每个浮标的音频与频谱图（spectrogram）进行听觉与目视监测，以验证浮标工作是否正常。

关于声呐浮标的更多信息详见文件：TEMPO航次声呐浮标数据采集记录 - 2021-01-15.pdf

## 参考文献
1. Greene, C.R.J. 等, 2004. 海底记录仪中的定向频率与记录（DIFAR）传感器用于秋季洄游期间弓头鲸的定位. 《美国声学学会杂志》, 116(2), 第799–813页.
2. Miller, B.S. 等, 2016. 基于定向声呐浮标的须鲸叫声实时定位软件：以南极蓝鲸为例. 《美国声学学会杂志》, 139(3), EL83-EL89. 可访问: http://scitation.aip.org/content/asa/journal/jasa/139/3/10.1121/1.4943627
3. Miller, B.S. 等, 2015. 验证被动声学定位的可靠性：一种邂逅稀有且偏远的南极蓝鲸的新方法. 《濒危物种研究》, 26(3), 第257–269页. 可访问: http://www.int-res.com/abstracts/esr/v26/n3/p257-269/
4. Rankin, S., Miller, B., Crance, J., Sakai, T., and Keating, J. L. (2019). "Sonobuoy Acoustic Data Collection during Cetacean Surveys," NOAA Tech. Memo. NMFS, SWFSC614, 1–36.