Volume 129, Issue 5, May 2011
Index of content:
- ARCHITECTURAL ACOUSTICS 
The sound strength parameter G and its importance in evaluating and planning the acoustics of halls for musica)129(2011); http://dx.doi.org/10.1121/1.3573983View Description Hide Description
The parameter, “Strength of Sound G” is closely related to loudness. Its magnitude is dependent, inversely, on the total sound absorption in a room. By comparison, the reverberation time (RT) is both inversely related to the total sound absorption in a hall and directly related to its cubic volume. Hence, G and RT in combination are vital in planning the acoustics of a concert hall. A newly proposed “Bass Index” is related to the loudness of the basssound and equals the value of G at 125 Hz in decibels minus its value at mid-frequencies. Listener envelopment (LEV) is shown for most halls to be directly related to the mid-frequency value of G. The broadening of sound, i.e., apparent source width (ASW) is given by degree of source broadening (DSB) which is determined from the combined effect of early lateral reflections as measured by binaural quality index (BQI) and strength G. The optimum values and limits of these parameters are discussed.
On the efficacy of spatial sampling using manual scanning paths to determine the spatial average sound pressure level in rooms129(2011); http://dx.doi.org/10.1121/1.3573986View Description Hide Description
In architectural acoustics, noise control and environmental noise, there are often steady-state signals for which it is necessary to measure the spatial average, sound pressure level inside rooms. This requires using fixed microphone positions, mechanical scanning devices, or manual scanning. In comparison with mechanical scanning devices, the human body allows manual scanning to trace out complex geometrical paths in three-dimensional space. To determine the efficacy of manual scanning paths in terms of an equivalent number of uncorrelated samples, an analytical approach is solved numerically. The benchmark used to assess these paths is a minimum of five uncorrelated fixed microphone positions at frequencies above 200 Hz. For paths involving an operator walking across the room, potential problems exist with walking noise and non-uniform scanning speeds. Hence, paths are considered based on a fixed standing position or rotation of the body about a fixed point. In empty rooms, it is shown that a circle, helix, or cylindrical-type path satisfy the benchmark requirement with the latter two paths being highly efficient at generating large number of uncorrelated samples. In furnished rooms where there is limited space for the operator to move, an efficient path comprises three semicircles with 45°–60° separations.
Absorption of a rigid frame porous layer with periodic circular inclusions backed by a periodic grating129(2011); http://dx.doi.org/10.1121/1.3561664View Description Hide Description
The acoustic properties of a periodic rigid frame porous layer with multiple irregularities in the rigid backing and embedded rigid circular inclusions are investigated theoretically and numerically. The theoretical representation of the sound field in the structure is obtained using a combination of multipole method that accounts for the periodic inclusions and multi-modal method that accounts for the multiple irregularities of the rigid backing. The theoretical model is validated against a finite element method. The predictions show that the acoustic response of this structure exhibits quasi-total, high absorption peaks at low frequencies which are below the frequency of the quarter-wavelength resonance typical for a flat homogeneous porous layer backed by a rigid plate. This result is explained by excitation of additional modes in the porous layer and by a complex interaction between various acoustic modes. These modes relate to the resonances associated with the presence of a profiled rigid backing and rigid inclusions in the porous layer.
Relation between annoyance and single-number quantities for rating heavy-weight floor impact sound insulation in wooden houses129(2011); http://dx.doi.org/10.1121/1.3561660View Description Hide Description
This study investigated the relation between annoyance and single-number quantities to rate heavy-weight floor impactsound insulation. Laboratory experiments were conducted to evaluate the subjective response of annoyance resulting from heavy-weight floor impactsounds recorded in wooden houses. Stimuli had two typical spectra and their modified versions, which simulate the precise change in frequency response resulting from insulation treatments. Results of the first experiment showed that the Zwicker’s percentile loudness (N 5) was the quantity to rate most well annoyance of heavy-weight impactsound over a wide sound level range. The second experiment revealed that arithmetic average (L iFavg,Fmax) of octave-band sound pressure levels measured using the time constant “fast” and Zwicker’s percentile loudness (N 5) much better described annoyance by the precise change in the sound spectrum attributable to insulation treatments than Japanese standardized single-number quantities (L i,Fmax,r, L iA,Fmax, and L i,Fmax,Aw) do. Japanese standardized single-number quantities using the A-weighting curve as a rating curve were found to be excessively influenced by the 63 Hz octave-band sound level and have the great sound level-dependences in the relation with subjective ratings.