Relation of acoustical parameters with and without audiences in concert halls and a simple method for simulating the occupied state

Five acoustical parameters-reverberation time RT, early decay time EDT, cla rity C-80, strength G, and interaural cross-correlation coefficient IACC-we re measured using identical procedures with and without audiences in six co ncert and opera halls. Reverberation times without audiences were measured in 15 additional halls using the same measuring techniques as for the six h alls above, but for full occupancy the data were taken from musical stop ch ords at symphonic concerts. This paper shows that in all halls (1) the occu pied RT can be predicted from the unoccupied RT using a linear regression e quation, y = a - b exp(x), within acceptable limits, at low- and mid-freque ncies. It is also shown for the six halls that (2) occupied C-80's are pred icted accurately from unoccupied values by the newly proposed equation; (3) G's with and without audiences are highly correlated by a first degree lin ear regression equation; and (4) IACCs have nearly the same value in both o ccupied and unoccupied halls. As a separate subject, the successful use of a cloth covering for seats in a concert or opera hall to simulate the occup ied condition has been developed. (C) 2001 Acoustical Society of America.