Determination of Reverberation Time and Sound Pressure Level of Selected Lecture Halls in University of Agriculture, Makurdi-Benue State, Nigeria

Abstract

Aim: Designing a lecture hall acoustics is a prestigious task which demands high accuracy of acoustical measures such as Reverberation time (T), Sound pressure levels (SPL) among other numerous parameters. In Nigeria however, little is considered about the acoustical environment on stages in lecture halls and how the design of environments are perceived by the users even though most international standards set optimum values of these parameters with respect to room volume and designed purposes. Study Design: This research has been conducted to examine the values of T and SPL of six selected unoccupied lecture halls in the University of Agriculture, Makurdi. Place and Duration: Department of Physics/ College of Science Federal University of Agriculture, P.M.B.2373 Makurdi-Benue State, Nigeria, between July 2017 to February 2018. Methodology: The linear dimensions (length, breadth and height) of each lecture hall and the surface areas of the absorbent materials per each lecture hall was measured using the measuring tape . The AutoCAD software was then used for volume computations. To measure the sound pressure levels (SPLs), equivalent sound pressure levels were registered at each selected point of the halls using a calibrated digital sound level meter (model Extech 407780) at wall distance of 1.00 m and intervals of 10 s in between. Results: Reverberation Time values were calculated using Sabine’s method. The mean value of T60 was found to be 1.66 s with a standard deviation of 0.36 s. The calculated SPL values were found to have a least value of 63.68 dB (A) in L4 while L6 has the highest value of a dispersion of 84.79 dB (A). In comparison with international guidelines, the reverberation time as well as SPL values found in these lecture halls were not within reference values of 0.40 ≤ T60 ≤ 0.80s and 35dB(A)≤ SPL ≤ 45dB(A) established by International Standard Organization (ISO) 3382, International Electro technical Commission (IEC) 60268 and World Health Organization WHO. Hence the results showed that the selected lecture halls do not meet the current standard of acoustic design set for public speech buildings.