Raw data for the results from the scale model investigations are now also freely available, see the Project data page for more information and download link.
I have uploaded results for ST within octave bands without the standard reference level (previously not presented, see the Articles page. The reference level for ST is found to vary significantly between the stages studied. This appears to make it more difficult to compare levels of reflected sound levels between stages and between different source locations on individual stage – from measured ST.
This article also includes results for STlate within octave bands (previously not presented).
I have uploaded results for STlate within octave bands (previously not presented, but available as part of the project data zip file), see the above post.
The project data from the stage acoustics project covered on this site is now freely available, see the Project data page for more information.
I have written a new article providing some more details on stage and ensemble geometry related to masking effects. The main focus is how the size and proportions of an acoustic ensemble set requirements to the size and proportions of the stage enclosure or the room the ensemble performs in. Some background information with an overview of different stage enclosure designs in the vertical plane is also give. See the Articles page.
At the time my PhD thesis was completed Christopher Blair, both an acoustician and conductor, gave his views on acoustic conditions for symphony orchestra on a blog posting on the Adaptistration web site. Several other interesting blog postings by Blair are also available on this web site. I was unaware of his posting on acoustics for orchestras when I completed my thesis, so it appears that Blair’s views on beneficial conditions for an orchestra are independent from the results in covered in my thesis.
In the blog posting referred to above Blair writes: “The art of designing good on-stage acoustics boils down to providing just enough early energy to help with coordination, but not so much as to mask audibility of the late-energy room response.” This is in very good agreement with the conclusions from my PhD thesis: the main purpose of early reflections back to the orchestra was found to an effective compensation for low direct sound level within the orchestra. Additionally, the most popular venues covered in our research project had a certain balance between early and late acoustic response on stage (C80), as well as a certain level of the late acoustic response in the main auditorium (Glate).
Blair has previously written about the importance of reflections from the main auditorium reaching the stage, in the Journal of the Conductors Guild, Vol. 19, No. 2, 1998. In this article (unfortunately not freely available) the relevance of perceptual masking effects for perceived conditions is described, along with a study of plan and section drawing for a set of existing symphony orchestra venues. For popular stages there are identified reflections from the back section of the auditorium that reach the stage with delay(s) within typically 100–300 milliseconds. Unfortunately this article was not included in the literature review of my PhD thesis, but the conclusions in this article are also similar to my conclusions.
One of the major findings from the research project documented on this website was that low ceiling can be very problematic for a symphony orchestra. Recently a paper by Higini Arau-Puchades (Arau Acustica) has been published in Acta Acustica united with Acustica; Increasing the Acoustic Volume of Performance Spaces without Altering the Internal Dimensions. The cases covered in this paper suggest that a low ceiling is the major reason for difficult acoustic conditions experienced by the orchestras playing in their specific venues. The paper also includes a design of a grid of vertically oriented solid panels suspended above the orchestra, called an acoustic labyrinth. The picture below is taken from the mentioned paper.
The apparent effect of this construction is to block the direct reflection from the ceiling particularly above 500 Hz. Blocking the direct path results in the sound travel a longer path from the orchestra via the ceiling back down towards the orchestra, resulting in lower level and larger delay on the ceiling reflection. The grid also contributes to scatter the ceiling reflection into different directions. The ceiling of the actual venues had curved ceiling that focused the reflected sound down towards the orchestra. Blocking the direct reflection by the grid will in such cases have a very significant effect on the level of reflection sound from the ceiling.
The orchestras reported on a significantly improved acoustic conditions with the grid installed. This is very encouraging since it suggests that there can be a cost-effective alternative to improve conditions for orchestras under a low ceiling. Raising the ceiling physically will in most cases be too expensive to be feasible.
There are only given a few suggestions in the paper to why the grid improves the perceived conditions. Apparently the experienced improvement can largely be explained by the findings from my PhD thesis; a high ceiling was here found beneficial for avoiding loud instruments becoming too loud and contributing to make the string section and the acoustic response from the main auditorium audible to the whole orchestra. This conclusion was based on comparing acoustic conditions with the orchestra present on stage, related to the psycho-acoustic effects masking, precedence effect and the cocktail-party effect. The real stages studied in the PhD also supported this conclusion.
It will be interesting to hear more about the players’ experiences with Arau-Puchade’s grid in the future. To further understand the effect of the grid it would be very interesting to see measured acoustic responses in detail and results for Glate and C80, both on stage and in the main auditorium for these venues – not only Schroeder curves, T30, G and STearly on stage.