Monaural (adjective)

1. Relating to or involving the use of only one ear.
2. Involving or produced by a single channel of audio.

Origin:

From the word "mono-" meaning one and "aural" meaning of or relating to the ear.

Examples:

1. A monaural telephone does not require a headset and can be held to one ear.
2. The monaural recording was made with only one microphone.
3. The monaural sound system was not able to produce a stereo effect.
4. He preferred monaural music as it was simpler and more natural.
5. The monaural headphones only had one speaker and were less expensive.