Automixer
An automixer, also known as an automatic mixer or auto mixer, is an audio processing device or software plugin that automatically controls the gain of multiple microphone signals. Its primary function is to reduce background noise and reverberation in multi-microphone environments, typically by attenuating (reducing the volume of) the signals from microphones that are not actively picking up the desired sound source, while boosting or maintaining the gain of the active microphone(s).
Automixers are commonly used in applications such as:
- Conferencing: To improve the clarity of speech during teleconferences and video conferences.
- Houses of Worship: To manage the levels of multiple microphones used by speakers, choirs, and instrumentalists.
- Broadcast: To control the levels of microphones used in panel discussions and interviews.
- Courtrooms and Government Meetings: To ensure clear and intelligible recordings of proceedings.
- Theatrical Productions: To manage the gain of multiple stage microphones.
The core principle behind an automixer is to identify the "active" microphone(s) – those picking up the primary sound source – and prioritize their signals. This is often achieved through various algorithms, including:
- Gain Sharing: Distributes gain across multiple microphones, with the active microphone receiving the most gain.
- Nom Attenuation: Attenuates all inactive microphones by a certain amount, typically a fixed number of decibels (dB).
- Gate/Threshold Based: Opens the microphone channel when the signal level exceeds a set threshold and closes it when the signal falls below the threshold. This method can sometimes lead to abrupt and noticeable changes in gain.
- Priority Assignment: Assigns priority levels to individual microphones, allowing certain microphones to override others.
Modern automixers often incorporate advanced features such as:
- Adaptive Gain Control: Automatically adjusts gain based on the ambient noise level.
- Feedback Suppression: Reduces the risk of audio feedback loops.
- Noise Reduction: Further reduces unwanted background noise.
- Ducking: Automatically lowers the volume of other audio sources when speech is detected.
Automixers can exist as dedicated hardware units, software plugins for digital audio workstations (DAWs), or as integrated features within digital mixing consoles. They are designed to simplify the mixing process and provide a consistent and professional audio output in situations with multiple microphones.