An audio mode where sound is played through a single channel rather than separated left and right channels (monaural); contrasted with stereo.
古いラジオの音源はモノラルで録音されていることが多い。
Audio sources on old radios are often recorded in monaural.
録音設定をモノラルに切り替えてテストしてみよう。
Switch the recording setting to mono and test it.