Flame Scanners; Pulsation Frequency

My 12-May, 4:17pm response omitted an important factor:

Flame instability results in combustion chamber (firebox, furnace)pressure variations. Hence, the perception of low frequency acoustical pulsations" or "breathing." Sometimes a whisper, other times a roar.

Phil Corso, PE
Trip-A-Larm Corp
I have experience before for burner system in Boiler and Chemical area and we are using flame detector FIREYE or DURAG. Hope this information can help you.
Best Regard, Herry PT. Tanjung Enim Lestari