Understanding Audio Feedback

What is Feedback? Feedback is the result of a microphone picking up sound emitted by a speaker, which is then amplified and re-emitted in a loop. This loop can escalate until it becomes a high-pitched squeal or a distorted hum. Feedback can occur in any live sound system and is usually disruptive in performance settings. Understanding its causes and frequencies is essential for effective management. The Science Behind Feedback: When a microphone picks up sound from the speaker, it sends that sound through the amplifier and back through the speaker. The more the sound is amplified, the more the mic picks up the sound from the speaker, and this cycle creates feedback. Frequency Range of Feedback: Feedback can occur across a wide frequency range, but it tends to be most noticeable within the midrange and high frequencies because human ears are more sensitive to those frequencies. Low-Frequency Feedback (100-250 Hz): Often caused by powerful bass sounds or large subwoofers. This type of feedback manifests as a low rumble and can be difficult to locate. Mid-Frequency Feedback (500 Hz - 1 kHz): Usually found in smaller rooms with reflective surfaces, this feedback is often more pronounced and resembles a "honk" or "squawk." High-Frequency Feedback (2 kHz - 8 kHz): This type of feedback is sharp and piercing and is most often associated with condenser microphones or high-sensitivity mics. It’s particularly troublesome when using high-gain settings in sensitive environments. Identifying Feedback Frequencies: To properly manage feedback, it’s essential to identify the exact frequencies involved. Using tools such as real-time analyzers (RTAs) or frequency analyzers can help pinpoint problem frequencies during sound checks. You can also employ a parametric EQ to boost or cut specific frequencies and identify where the feedback is coming from.