Described herein is an audio watermarking technology for detecting watermarks in audio signals, such as a music clip. Instead, the beam shaping element enlarges the size of the area of illumination on the array slightly, and mixes, or homogenizes, the light. At an ignition by the spark plug, high-frequency square wave signals are generated by an oscillator after an ignition signal is cut off. The unbonded flexible pipe further includes a galvanic barrier layer between the first and the second tensile armoring layer. The severing creates a through-hole in the board. Frequency analysis of a heart rate measurement and a heartbeat interval measurement of a subject is performed to determine a high-frequency index, a low-frequency index and a ratio therebetween.