Same as the previous file, but I have tried to remove some of the background noise using a LP filter at around 1kHz in Audacity. Sounds below 40Hz have also been removed.
I tried Audacity's Noise Reduction. It did reduce the noise level, but introduced artifacts. So I decided not to use. 神秘不和諧的哼唱LP 1 kHz.wav 聲道:2 類型:wav dissonant、humming、mysterious、night、strange、recording、unknown 不搭調、低唱、神秘、晚、奇怪、記錄、未知 資料來源:freesound ( https://freesound.org )