Verification note: Results are design aids, not stamped engineering or code approval. Always check the current project specification, adopted code, manufacturer data and latest edition of the cited standard before construction or procurement.

AUDIO

Feedback Calculator

PAG/NAG feedback margin estimator for speech reinforcement.

Best for concept-stage speech systems. Always validate gain-before-feedback on the real room, real loudspeaker pattern and actual microphone type.

Gain-before-feedback estimator

D0 — speaker to microphone (m)

D1 — talker to microphone (m)

Ds — talker to far listener (m)

D2 — loudspeaker to far listener (m)

Open microphones (NOM)

Enter values and calculate.

PAG = 20log(D0) − 20log(D1) + 20log(Ds) − 20log(D2) − 10log(NOM) − 6 dB
NAG = 20log(Ds) − 20log(D2)
Feedback margin = PAG − NAG

WORKED EXAMPLE

Example — paging loudspeaker and lectern mic

The diagram shows the distances used in the classical potential-acoustic-gain and needed-acoustic-gain approach. Higher D0 and lower D1 usually improve available gain.

Source details

AVIXA PAG/NAG guidance.
AV Systems Performance Verification Guide — gain-before-feedback concepts.