Acoustical effects of columns, beams and furniture on sound fields in small enclosures
In acoustic design of small enclosures, it is a considerably important matter to control eigenmodes at low frequencies, so that many researches have been done on the effect of overall shapes of rooms on the eigenmodes, such as optimization of room dimensions ratio. However, overall room shapes are usually restricted to rectangular forms due to easy construction, therefore it is desirable to improve sound fields only by changing partial elements in rectangular rooms. In the present paper, the effects of additional elements, such as columns, beams and furniture, on the sound field in a small rectangular room are investigated through wave-based numerical analysis. Supposing a room for listening use with a loudspeaker, the effects are evaluated regarding the flatness of frequency response and the uniformity of spatial distribution in a listening area. The results show that: the effect of columns is small but more than beams; that of closed-type shelves is relatively large but not so much as open-type shelves; the size and the arrangement of every element have unnegligible effects. It is also seen that the additional elements generally lead to positive effects in flatness of frequency response and special uniformity even at low frequencies, although in a specific case.
The effect of a mixing console on the monitoring response in a mixing room
Mixing consoles, which are usually of large dimensions, are essential equipment in a mixing room of a production studio. This large obstacle always has to be placed nearby the listening position in a mixing room. A significant dip at around 100 Hz is often observed on the monitoring response, the transfer function from the loudspeaker to the listening position, in a small/medium sized mixing room. This paper studies the relationship between the dip at around 100 Hz and the effect of the presence of the mixing console. The generating mechanism of the dip is investigated by numerical simulations and experimental measurements. The results show that the reflection sound from the floor and the behavior of the mixing console as a cross over filter are important when considering the dip. Examples of trials for improvement of the dip are also examined.
Predicted and Measured Low Frequency Response of Small Rooms
The sound level difference of party walls at low frequencies [25–200 Hz] has been shown to be strongly dependent on the modal characteristics of the sound fields of the separated rooms. The modal characteristics can be modelled by numerical methods and a Finite Element Method has been selected to model sound transmission between adjacent rooms separated by a party wall. The numerical eigenfrequencies were compared with the theoretical eigenfrequencies to select a mesh model for which the eigenfrequencies are processed within an acceptable error range. As a prelude to the study of sound transmission between dwellings, the simulation of one single room, modelled with the selected mesh model, was validated by predicting the frequency response and comparing values with measured frequency response of a 1:4 scale room model. Results show promising agreement and establish the reliability of the work.