MONITORING THE ACOUSTIC ACTIVITY OF A PHARMACEUTICAL POWDER DURING ROLLER COMPACTION

Acoustic relaxation emissions (ARE) from microcrystalline cellulose (M C) and maize starch (MS) were detected during roller compaction using a microphone with flat frequency response up to 20 kHz and a tunable h igh pass filter the limiting frequency of which was set at 15 kHz. The noise from the compactor itself was found to appear mainly below 15 k Hz. The ARE intensity of MC was observed to increase as a function of applied compressive force up to 45 kN, while the ARE intensity-force c urve of MS had a maximum at 50 kN. A Gaussian-shaped function fitted r easonably to the data in both cases. (C) 1997 Elsevier Science B.V.