This document summarizes research on measuring time domain sound spectra in a ducted axial fan under stable operating conditions. The fan test setup and instrumentation are described, including a microphone to capture sound signals, data acquisition system, and LabVIEW software to analyze spectra. Experiments were conducted at varying rotor speeds from 2400-3600 rpm with a throttle position of 6 cm. Results showed that sound pressure amplitude generally increased with rotor speed and fluctuated periodically due to fan blade passage. Maximum amplitudes ranged from 16-36 dB depending on rotor speed. The time domain spectra measurements provide insights into fan acoustics and stability characteristics.