|
Room acoustics describes how sound behaves in an enclosed space. The way that sound behaves in a room can be broken up into roughly four different frequency zones: *The first zone is below the frequency that has a wavelength of twice the longest length of the room. In this zone, sound behaves very much like changes in static air pressure. *Above that zone, until the frequency is approximately 11,250(RT60/V)1/2 (when Volume is measured in cubic feet and 2000(RT60/V)1/2 when Volume is measured in cubic metres),〔"Sound System Engineering" 4th edition, Don Davis, Eugene Patronis, Pat Brown, June 2013, page 215〕 wavelengths are comparable to the dimensions of the room, and so room resonances dominate. This transition frequency is popularly known as the Schroder frequency, or the cross-over frequency and it differentiates the low frequencies which creates standing waves within small rooms from the mid and high frequencies.〔"Handbook of Noise and Vibration Control", Malcolm J. Crocker, 2007, page 54〕 *The third region which extends approximately 2 octaves is a transition to the fourth zone. *In the fourth zone, sounds behave like rays of light bouncing around the room. ==Natural modes== The sound wave has reflections at the walls, floor and ceiling of the room. The incident wave then has interference with the reflected one. This action creates standing waves that generate nodes and high pressure zones.〔“Acoustics”, Leo Beranek, chapter 10, McGraw Hill Books, 1954〕 In 1981, in order to solve this problem, Oscar Bonello, professor at the University of Buenos Aires, formulated a modal density concept solution which used concepts from psychoacoustics.〔"A NEW CRITERION FOR THE DISTRIBUTION OF NORMAL ROOM MODES" - Journal of the Audio Engineering Society (USA) Vol. 29, Nro. 9 - September/1981. Oscar Bonello〕 Called "Bonello Criteria", the method analyzes the first 48 room modes and plots the number of modes in each one-third of an octave. The curve increases monotonically (each one-third of an octave must have more modes than the preceding one).〔''Handbook for Sound Engineers'' Glen Ballou, Howards Sams Editors, page 56.〕 Other systems to determine correct room ratios have more recently been developed 〔Cox, TJ, D'Antonio, P and Avis, MR 2004, "(Room sizing and optimization at low frequencies )." , Journal of the Audio Engineering Society, 52 (6) , pp. 640-651.〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「room acoustics」の詳細全文を読む スポンサード リンク
|