The measurement of impulse responses inside of a room or a theatre is a critical task in architectural acoustics. The impulse responses are usually measured using either Exponential Sine Sweep (ESS) or Maximum Length Sequence (MLS) signals. The theory behind MLS generation and use is well developed and does not involve computational problems. When a non-linear system is measured, the distortion appears in the deconvolved impulse response as a series of peaks distributed over time, in deterministic positions. In case of presence of noise during the measurement, the phase of any spurious noise, even an impulsive one, is randomly distributed over the entire length of the recovered impulse response. The ESS signal shows some advantages over MLS, such as a better signal to noise ratio (SNR) and a robust non-linearity rejection. Typically, in the same conditions, the ESS has a dynamic range of about 15dB higher than MLS. Nonetheless, the generation of an ESS signal and the subsequent analysis of impulse responses involve some problems whose solutions are not yet common practice and short impulsive noises can contaminate the sampled data, causing bad effects on the deconvolved impulse response, in form of a frequency decreasing sweep. For the above mentioned reasons ESS is generally more suitable than MLS for use in architectural acoustics, but in some cases the use of MLS signal is still to be preferred. Differences and advantages between impulse response measurements obtained by means of MLS or ESS, are analyzed and discussed in this paper and an in-depth analysis of both measurement methods is presented. Some case studies of impulse response measurements performed inside historical Italian opera houses using both MLS and ESS, in non-ideal conditions (for example in presence of spurious noise), are presented and examined, highlighting differences, advantages and pitfalls of both measurement methods

The foundation of architectural acoustics as an independent science is generally referred to Sabine’s early studies and their application. Nevertheless, since the 16th Century, a great number of authors wrote essays and treatises on the design of acoustic spaces, with a growing attention to the newborn typology of the Opera house, whose evolution is strongly connected to the cultural background of the Italian peninsula. With roots in the Renaissance rediscovery of Vitruvius’s treatise and his acoustic theory, 16th- to 19th-Century Italian authors tackled several issues concerning the construction of theatres—among them, architectural and structural features, the choice of the materials, the social meanings of performances. Thanks to this literature, the consolidation of this body of knowledge led to a standardisation of the forms of the Italian Opera house throughout the 19th Century. Therefore, the scope of this review paper is to focus on the treatises, essays and publications regarding theatre design, written by pre-Sabinian Italian scholars. The analysis of such literature aims at highlighting the consistencies in some 19th-Century minor Italian Opera houses, in order to understand to what extent this scientific and experimental background was part of the building tradition during the golden age of the Italian Opera.