The source level (SL) and vocalizing source depth (SD) of individuals from two blue whale (BW) subspecies, an Antarctic blue whale (Balaenoptera musculus intermedia; ABW) and a Madagascar pygmy blue whale (Balaenoptera musculus brevicauda; MPBW) are estimated from a single bottom-mounted hydrophone in the western Indian Ocean. Stereotyped units (male) are automatically detected and the range is estimated from the time delay between the direct and lowest-order multiply-reflected acoustic paths (multipath-ranging). Allowing for geometric spreading and the Lloyd's mirror effect (range-, depth-, and frequency-dependent) SL and SD are estimated by minimizing the SL variance over a series of units from the same individual over time (and hence also range). The average estimated SL of 188.5 ± 2.1 dB re $1\mu \text{Pa}$ measured between [25–30] Hz for the ABW and 176.8 ± 1.8 dB re. $1\mu \text{Pa}$ measured between [22–27] Hz for the MPBW agree with values published for other geographical areas. Units were vocalized at estimated depths of 25.0 ± 3.7 and 32.7 ± 5.7 m for the ABW Unit A and C and, $\simeq 20$ m for the MPBW. The measurements show that these BW calls series are stereotyped in frequency, amplitude, and depth.

中文翻译：

---

单传感器观测对西印度洋两个蓝鲸亚种的声源水平和发声深度估计

来自两个蓝鲸 (BW) 亚种、南极蓝鲸 ( Balaenoptera musculus intermedia ; ABW) 和马达加斯加侏儒蓝鲸 ( Balaenoptera musculus brevicauda ) 个体的声源水平 (SL) 和发声源深度 (SD); MPBW）是根据印度洋西部的一个底部安装的水听器估计的。定型单元（男性）被自动检测到，距离是从直接和最低阶多重反射声路径（多径测距）之间的时间延迟估计的。考虑到几何扩展和劳埃德镜效应（范围、深度和频率相关），SL 和 SD 是通过最小化同一个体随时间（因此也是范围）在一系列单位上的 SL 方差来估计的。平均估计 SL 为 188.5 ± 2.1 dB re$1\mu \text{帕}$ 在 ABW 的 [25–30] Hz 和 176.8 ± 1.8 dB re 之间测量。 $1\mu \text{帕}$在 [22–27] Hz 之间测量的 MPBW 与其他地理区域公布的值一致。对于 ABW 单元 A 和 C，单元在 25.0 ± 3.7 和 32.7 ± 5.7 m 的估计深度发声，$\simeq 20$m 为 MPBW。测量结果表明，这些 BW 呼叫系列在频率、幅度和深度上都是固定的。