Alessandro Cocchi

Reliability of scale-model researches: a concert hall case

Abstract To verify the reliability of acoustical tests on concert halls performed by means of scale models, a quality evaluation has been carried out on a recently constructed concert hall in accordance with the Ando methodology. A scale model has been made of the same concert hall in which the effects of some modifications of the ambient geometry were examined both from the objective standpoint and from the viewpoint of the subjective acoustical quality. This paper shows the results obtained in the above-mentioned research.

Possible correlation between acoustic and thermal performances of building structures

Most European standards required high performance values for sound and thermal insulation in building structures, according to Directive EEC 89/106. Sound transmission and heat transfer in structures have different physical and analytical approach and specific parameters of performance (i.e. sound transmission loss or thermal transmittance) are not directly correlated each others; many kind of structures have also different behaviour depending on mechanical properties of materials, numbers of layers of materials, etc. The aim of this work is to analyse possible correlation between sound transmission performances and thermal properties values in order to evaluated common trends related to physical properties of the various building components, like for example density or surface mass.

Investigation on the flanking transmission of impact sound insulation of floor

Impact sound pressure level of floors depends, as general rule, on direct sound radiated by the floor excited by a standard tapping machine and on flanking transmission of lateral walls. Depending on the kind of junction between the floor and walls of the receiving room, flanking paths can be more or less important. Requirements of laboratory test specimens are not well specified in EN ISO 140 standards, particularly for junctions of the test floor and lateral walls. In this paper measurements performed at DIENCA laboratory are presented in order to evaluate the influence of flanking transmission on impact sound pressure levels of a standard floor and on impact sound reduction level of standard floor with a resilient layer. Measurements are performed on a 14‐cm‐thick concrete floor in two different conditions: first connected on two sides of the receiving room and then on all four sides. Impact sound pressure levels and vibration levels are analyzed in order to evaluate the contribution of different transmission paths. As the measurements were carried on in the new facility for measurement of the contribution of the flanking transmission, this facility will be exhaustively presented in the paper.

A virtual reconstruction of the trumpet

Virtual reconstructions of musical/instruments have already been analyzed in past years on violins. The ‘‘virtual’’ instruments can be used in subjective listening tests for the evaluation of the sound quality of different instruments, as well as in the restoration of ancient instruments, and for preliminary listening tests on new designed instruments. In this paper, the trumpet is treated as a linear system, characterized by its impulse response. From the IRs measured in different positions in the trumpet, an inverse numeric filter of three trumpets has been obtained, through a new developed technique. From the recording of some original pieces of music, sampled directly inside one of the trumpets, an ‘‘anechoic’’ signal has been obtained by convolution with the inverse filter calculated in the same position. The ‘‘anechoic’’ signal, convolved with the IRs just measured in the other trumpets, produced a signal containing all the acoustic characteristics of the instruments, avoiding all nonacoustic phenom...

Italian opera house Mantua's Teatro Scientifico acoustical parameters measurements' comparison between Neumann KU 100 and Schoeps KFM 6 binaural recording systems

From the dawning of modern acoustics, researchers tryed to develop useful measurement techniques to describe acoustical field. Sound field measurement improvements first endeavours implementing microphone capsule miniaturization technology date back to the thirtyes of the past century. Long human perception reproduction path through recording tecnique came to the attempt to position transducers similarly to the human natural hearing system, frequently obtaining as alluring results as difficult comparison among them and reapply. This paper describes processes, first results and comparison between as much as possible identical acoustical measurement sessions in Mantuas Teatro Scientifico opera house using Neumann KU 100 and Schoeps KFM 6 binaural recording systems at the same time.

Acoustical qualification of Teatro Nuovo in Spoleto before refurbishing works

To qualify the acoustical quality of an opera house two different approaches are now available: one is based on responses of qualified listeners (subjective judgments) compared with objective values of selected parameters, the other on comparison tests conducted in suited rooms and on a model of the auditory brain system (preference). In the occasion of the refurbishment of an opera house known for the Two Worlds Festival edited yearly by the Italian Composer G. C. Menotti, a large number of measurements were taken with different techniques, so it is possible to compare the different methods and also the results with some geometrical criterion, based on the most simple rules of musical harmony, now neglected as our attention is attracted to computer simulations, computer aided measurement techniques and similar modern methods. From this work some link between well known acoustical parameters (not known at the time when architects sketched the shape of ancient opera houses) and geometrical criteria (well k...

Boxes and sound quality in an Italian opera house

The sound field in the boxes of an 18th century Italian opera house was studied by means of binaural measurements and computer simulations. The differences in listening between the boxes and the stall is best described by the values of ITDG, clarity, and spatial criteria resulting from the measurements. The periodic variation of the ITDG along the boxes depends also on the reflections coming from the ceiling. The best boxes for clarity and spatial impression are found in very different positions. Computer simulation supports these conclusions and helps in understanding the two different mechanisms by which the boxes influence the sound field in the hall: the equivalent sound absorption of the boxes and the periodic structure of the box‐covered walls. A validated computer model allows one to forecast how the sound field in the historical theater could be if some interior lining were added to the boxes, trying to restore the velvet lining which was supposed to exist in ancient times.

Material and obsolescence on flute tone quality

The rule of material and obsolescence on flute tone quality has been discussed for a long time among musicians and flute makers. Mozart himself made use of crystal flutes in some of his works (Rondo’, K617, Adagio, K356). From an acoustical point of view, since Boehm’s work of 1832, the effect of material on flute tone quality has not been investigated, until researches of recent years [Coltman (1971); Chapuis (1991)]. In this work the research has been carried out measuring impulse responses inside the tube of the flute. Two different flutes have been utilized, i.e., a light‐alloy flute and a silver flute. The MLS sequences, with homemade software, have been utilized, gathering impulse responses in two different positions in the tube, in order to verify the variation of sound field. From the impulse responses a frequency analysis has been obtained, which pointed out that the silver flute contains more high frequency and shorter transient than the light‐alloy flute. Starting from the impulse responses, so...

Evaluation of the flanking transmission in a scale model of two adjoining rooms

Flanking transmission is the sound propagation through the lateral structures of two adjoining rooms. Evaluation of this transmission is possible with a statistical model of two rooms that considers mainly the reduction in vibration transmission between the partition and the lateral structures. With this model, which is the object of a project of international standard (Pr EN 12354), it is possible to evaluate the transmission through each path, considered independent of each other. The research carried out at the Acoustics Laboratory of the University of Bologna has validated the CEN model by measuring the vibration reduction index and the sound transmission in a scale model. The vibration transmission index has been measured both with transient and steady excitation of the structures, the first by means of a hammer and the second of an electromagnetic shaker. The sound reduction index of each path of transmission has been calculated measuring the mean pressure level in the source room and the mean vibra...

Acoustic behavior of a tense‐structure

During the design of a concert hall, the acoustical behavior of the sound field is often investigated by using numerical models. In the case of a restoration of the hall, or during the design of the orchestra chamber, acoustic measurements of impulse responses in the hall give precious information on the sound fields, e.g., RT, clarity, and so on. By using numerical simulation, it is then possible to verify the efficiency of the acoustic solution. Much commercial software is available, all of them following the geometric assumptions, as the Eikonal equation, while the diffraction and diffusion of sound are not usually taken into account, and all of them require the absorption coefficient of the walls. The tense‐structure, on the other hand, is not so easy to model, owing to the peculiar characteristics, i.e., modal behavior and impossibility to measure the absorption of the membrane. In this paper, the design of an acoustic intervention in a tense‐structure is shown. A procedure to find out the ‘‘equivale...