Abstract:
Organic material in sound insulation offers additional environmental and
human health benefits. This study deals with an experimental investigation of
the Sound Transmission Coefficient (STC) of loosely packed wood chips for
introduction as sound insulation applications. STC is calculated by measuring
the Transmission Loss (TL) through wood chips between the walls of the
cubical-shaped box. The material is packed securely between the walls of 5
cm thickness of a meshed cube of outer measurements 60×60×60 cm3. The
sound source is placed at the center of the cube. Packing uniformity is ensured
by stuffing the material evenly in known mass in a unit volume. The sound
source consists of a B&K type 4292, Omni directional speaker and a type 2734
amplifier. B&K type 2250 class 1 handheld Sound Level meter is used for
Sound Pressure Level measurements. SPL, inside and outside the cube, was
measured for four sides, and the average value was taken. Measurements were
taken in a reverberation room with 25 Hz ambient noise or less. Pink noise
(12.5 Hz –20,000 Hz) in one-third of octave bands is used for the study. TL
and STC were calculated, and variations were analyzed for different sound
frequencies. The results imply the TL of the material is significantly dependent
on the sound frequency. Sounds of frequencies less than 400 Hz are
transmitted with minimum attenuation, while higher-frequency sounds
significantly attenuate. These loosely packed wood chips efficiently weaken
the susceptible sound frequencies (2 to 4 kHz) to the human ear. The average
sound absorption coefficient in commercially available solid wood panels is
much less, with a higher reflection. Because of their flexibility, the loosely
packed sound insulation panels are not very attractive in the construction
industry. However, loosely packed, durable organic materials could be used in
the acoustic insulation industry in an creative manner, providing an esthetic
appearance to the room while maintaining good health.
