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

De invloed van het orkest op de akoestiek van de podiumomgeving The influence of the orchestra on stage acoustics

Abstract The available stage acoustic parameters measure the energy ratio between certain time intervals derived from an impulse response. The parameter time intervals may be based on typical sound paths on a stage. A study of typical sound paths and their time intervals indicates that a transition time point may exist between early reflected sound and late reflected sound at approximately 100 ms and that this transition time point is measured relative to the 'departure' of the sound from the sound source. However, the current choices for the time intervals in the available parameter formulas do not agree. There are two types of transition time points that reflect certain stage acoustical aspects related to a stage for a symphonic orchestra. The first is the transition time point between direct sound and reflected sound 'x' and the second is the transition time point between the early reflected sound and late reflected sound 'y'. The effect of the choice of transition time points is investigated for G x-y , G y-inf and LQ x-y from measured impulse responses. It is shown that the direct sound should be omitted to measure differences between halls and that different choices of time intervals do not result in large differences in the ranking of 7 concert hall stages. All parameters are commonly determined on an unoccupied (empty) stage, preferably with chairs and stands. In this paper, results of measurements on an occupied stage are presented which show large differences between empty and occupied stages. These measurements also indicate that a fixed time interval relative to the time of departure of the sound seems most appropriate

The effective air absorption coefficient for predicting reverberation time in full octave bands

A substantial amount of research has been devoted to producing a calculation model for air absorption for pure tones. However, most statistical and geometrical room acoustic prediction models calculate the reverberation time in full octave bands in accordance with ISO 3382-1. So far, the available methods that allow calculation of air absorption in octave bands have not been investigated for room acoustic applications. In this paper, the effect of air absorption on octave band reverberation time calculations is investigated based on calculations. It is found that the approximation method, as described in the standard ANSI S1.26, fails to estimate accurate decay curves for full octave bands. In this paper, a method is used to calculate the energy decay curve in rooms based on a summation of pure tones within the band. From this decay curve, which is found to be slightly concave upwards, T20 and T30 can be determined. For different conditions, an effective intensity attenuation coefficient mB;eff for the full octave bands has been calculated. This mB;eff can be used for reverberation time calculations, if results are to be compared with T20 or T30 measurements. Also, guidelines are given for the air absorption correction of decay curves, measured in a scale model

How orchestra members influence stage acoustic parameters on five different concert hall stages and orchestra pits

Stage acoustic parameters aim to quantify the amount of sound energy reflected by the stage and hall boundaries and the energy decay over time. In this research, the effect of orchestra presence on parameter values is investigated. The orchestra is simulated by dressed mannequins, which have been compared with humans with respect to acoustic properties. Impulse response measurements were performed in a concert hall, a theatre, a rehearsal room, and in two orchestra pits. Conditions were empty stage floors, stage floors with music stands and chairs only, and floors occupied by the mannequin orchestra. Results show that the direct and reflected sound levels and the energy decay are significantly affected by the orchestra compared to an empty stage or a stage with chairs and stands only. Both the direct sound and early reflected sound levels are reduced by the orchestra with the distance. The late reflected sound level is reduced considerably more than can be expected based on Barron's revised theory. It can be concluded that measurements on a stage without the orchestra being present results in significant differences. A practical method is presented to perform a “musician friendly” stage acoustic measurement with a real orchestr