Why orchestral musicians are bound to wear earplugs: About the ineffectiveness of physical measures to reduce sound exposure

Symphony orchestra musicians are exposed to noise levels that put them at risk of developing hearing damage. This study evaluates the potential effectivity of common control measures used in orchestras on open stages with a typical symphonic setup. A validated acoustic prediction model is used that calculates binaural sound exposure levels at the ears of all musicians in the orchestra. The model calculates the equivalent sound levels for a performance of the first 2 min of the 4th movement of Mahler's 1st symphony, which can be considered representative for loud orchestral music. Calculated results indicate that risers, available space, and screens at typical positions do not significantly influence sound exposure. A hypothetical scenario with surround screens shows that, even when shielding all direct sound from others, sound exposure is reduced moderately with the largest effect on players in loud sections. In contrast, a dramatic change in room acoustic conditions only leads to considerable reductions for soft players. It can be concluded that significant reductions are only reached with extreme measures that are unrealistic. It seems impossible for the studied physical measures to be effective enough to replace hearing protection devices such as ear plugs

Project Ancient Acoustics Part 1 of 4 : a method for accurate impulse response measurements in large open air theatres

Selecting an appropriate method for measuring ‘normal’ indoor concert hall acoustics is always a trade-off between time, stimulus type, number of measurements and measurement quality. For ISO 3382 room acoustic parameters to be derived accurately from impulse responses, this tradeoff\u3cbr/\u3eaims at a certain minimum decay range. Previously, there have been many attempts to obtain room acoustical parameter values in ancient amphitheatres, using hand claps, balloons, fire crackers, blank pistols, deterministic signals played by loudspeaker sound sources, etcetera. However, results are presented mostly without describing or discussing the quality of the obtained impulse responses (IR’s). Part of the Ancient Acoustics research project was to find out how to accurately measure many open air impulse responses in accordance with the ISO 3382 standard, under restricted time and resource conditions. Practical ‘measurement training’ in a Dutch open air amphitheatre resulted in a measurement setup and procedure that would meet the predefined requirements for measuring ancient amphitheatres. To reduce measuring time, asynchronous\u3cbr/\u3emeasurements (without cables) were carried out using multiple microphones and recording devices, as well as multiple dodecahedron sound sources playing the stimulus signals simultaneously. In addition, speech intelligibility measurements were performed using a separate speech source. This finally led to more than 10,000 accurate impulse responses for three theatres. This part of the study will focus on the method used to perform such a large number of good quality measurements within a day per amphitheatre. We will discuss the effect of device\u3cbr/\u3eclock speed mismatch due to signal asynchronicity, sound source directivity errors, system variance by meteorological influences and the effect of background noise on the impulse response decay range, using the Impulse response to Noise Ratio (INR) and the Just Noticeable Difference (JND) as quality measures

Project Ancient Acoustics Part 1 of 4 : a method for accurate impulse response measurements in large open air theatres

Selecting an appropriate method for measuring ‘normal’ indoor concert hall acoustics is always a trade-off between time, stimulus type, number of measurements and measurement quality. For ISO 3382 room acoustic parameters to be derived accurately from impulse responses, this tradeoff\u3cbr/\u3eaims at a certain minimum decay range. Previously, there have been many attempts to obtain room acoustical parameter values in ancient amphitheatres, using hand claps, balloons, fire crackers, blank pistols, deterministic signals played by loudspeaker sound sources, etcetera. However, results are presented mostly without describing or discussing the quality of the obtained impulse responses (IR’s). Part of the Ancient Acoustics research project was to find out how to accurately measure many open air impulse responses in accordance with the ISO 3382 standard, under restricted time and resource conditions. Practical ‘measurement training’ in a Dutch open air amphitheatre resulted in a measurement setup and procedure that would meet the predefined requirements for measuring ancient amphitheatres. To reduce measuring time, asynchronous\u3cbr/\u3emeasurements (without cables) were carried out using multiple microphones and recording devices, as well as multiple dodecahedron sound sources playing the stimulus signals simultaneously. In addition, speech intelligibility measurements were performed using a separate speech source. This finally led to more than 10,000 accurate impulse responses for three theatres. This part of the study will focus on the method used to perform such a large number of good quality measurements within a day per amphitheatre. We will discuss the effect of device\u3cbr/\u3eclock speed mismatch due to signal asynchronicity, sound source directivity errors, system variance by meteorological influences and the effect of background noise on the impulse response decay range, using the Impulse response to Noise Ratio (INR) and the Just Noticeable Difference (JND) as quality measures

Project Ancient Acoustics Part 4 of 4 : stage acoustics measured in the odeon of herodes atticus and the theatre of argos

The stages of ancient theatres can be characterized by their circular shape called the ‘orchestra’, in front of a rectangular elevated stage with a highly decorated back wall. During some performances, a group of musicians was located in the circular shape, while actors were positioned on the elevated stage. In modern concert halls or theatres, acoustic support from the room is required for such performers to be able to play together properly. It can be assumed that in the ancient theatres, acoustic support must have been beneficial for performers as well. As part of the Ancient Acoustics project, stage acoustic measurements have been carried out in the Odeon of Herodes Atticus and the theatre of Argos. The goal of this paper, is to study the behavior of the early and late reflected sound level on ancient stages in their current state, measured by the extended early\u3cbr/\u3eand late support parameters STearly,d and STlate,d. Comparing the two stages is particularly interesting, because in Argos the back wall is missing. However, the absolute value of the parameters might have limited value because both the audience area and stage were unoccupied during the measurements. Also, the theatre of Argos has a severely damaged seating area and the back wall\u3cbr/\u3ehas not been restored, and at Odeon Herodes Atticus, the stage floor was missing. It is well known that the typical concentric shape of the audience area gives focused reflected sound back to the stage. This can be confirmed by the measured results that show a strong increase in reflected sound level when the source and receiver are positioned point-symmetrically along the center of\u3cbr/\u3ethe circle. This might have had an effect on performers, but whether the extra ‘support’ was beneficial is uncertain, because the ‘chirping’ and focussing of the reflected sound can cause colouration and poor balance

Project Ancient Acoustics Part 2 of 4 : large-scale acoustical measurements in the Odeon of Herodes Atticus and the theatres of Epidaurus and Argos

In the last decades we have seen an increased interest in the acoustics of ancient Greek and Roman theatres and much research has been performed on many of them. Research has mainly focused on modelling the acoustics of theatres and has shown various acoustical effects. However, only a limited number of in situ measurements have been available to validate the results. In this paper, results are presented of large-scale measurements which were performed in the Odeon of Herodes Atticus and the theatres of Epidaurus and Argos. The accuracy of these measurements is discussed in part one of this series of papers. Impulse response measurements have been conducted at respectively 200, 264 and 60 listener positions for 5 equal-angular dodecahedron sound source rotation steps at 2 source positions. In addition, binaural impulse responses were measured using an artificial head on respectively 10, 12 and 3 receiver positions. Finally, speech intelligibility measurements have been carried out in accordance with IEC 60268-16 using a ‘speech source’ that simulates a human voice. In the Odeon of Herodes Atticus, all measurements have been performed in the morning as well as in the evening, showing a minimal discrepancy well within the Just Noticeable Difference (JND) for every discussed parameter. This proves that it is legitimate to compare measurements collected during a full day under slightly different climate conditions. Results for the Odeon of Herodes Atticus show a uniform axisymmetric distribution over receiver positions of common acoustical parameters such as reverberation time, clarity, sound strength and spaciousness. For the theatre of Epidaurus this distribution is non-uniform due\u3cbr/\u3eto the opposite-facing seating areas, which is in line with findings from research by others. The results of the speech intelligibility measurements show a declining trend for STI over distance, which contradicts some findings presented in literature

Akoestiek van openluchttheaters in kaart gebracht

In het project ‘Ancient Acoustics’ zijn drie klassieke openluchttheaters akoestisch in kaart gebracht. Voor het uitvoeren van de metingen is een meetprocedure ontwikkeld waarbij een groot aantal impulsresponsies in korte tijd konden worden gemeten. Hierbij is in het bijzonder aandacht besteed aan de nauwkeurigheid van de meetresultaten. De resultaten van zowel de zitplaatsen als het podium zijn tot in detail gepresenteerd en vervolgens vergeleken met de resultaten van geometrische simulatiemodellen. In dit artikel vindt u de ‘highlights’ van dit onderzoeksproject