The acoustic characteristics of room environments can significantly influence speech levels and spectra, an aspect often overlooked in the current method for predicting speech privacy. This paper presents an investigation into the variability of speech spectra in various office contexts, with a specific focus on the influence of room type, communication medium, and language. The study involved over 70 workers in different office room types in Quebec, Canada, who participated in measuring speech spectra within those spaces. Two communication methods, in-person and video-conferencing scenarios, were utilized with participants using either English or French languages. The real-world scenarios shed light on the significant impact of various parameters on speech characteristics within office settings. Comparing the results with standardized speech levels and spectra from ASTM and ISO standards, derived from controlled environments like anechoic chambers, the study reveals significant differences when applying the standard speech spectra to actual office environments. Based on these findings, the study proposes potential modifications to the existing standards, aiming to enhance the accuracy of speech privacy and intelligibility predictions.

In the absence of government regulations, the Federation of Canadian Municipalities (FCM) and the Railway Association of Canada (RAC) espouse criteria for the assessment of vibration due to passing trains. Given that many municipalities follow these guidelines when considering the permitting of residential development, the effectiveness of the RAC vibration assessment methods are worth investigating. These include a limit of 0.14 mm/s RMS on amplitudes and a 75 m screening distance for triggering a detailed study of the impacts of railway vibration on developments in proximity to tracks. This paper provides a review of the criteria for their reasonableness at avoiding unwanted and/or undesirable vibration conditions for residential developments. This is accomplished through reference to the generic vibration propagation curves within the latest US Federal Railway/Transit Administrations noise and vibration guidelines and alternative parametric equations for estimating vibration propagation.

The Traffic Noise Model (TNM) is used to forecast traffic noise levels. When applied to federally funded projects, a user of the software is expected to apply "average" noise emissions for pavements. This "average" is an intermediate value that in some manner falls in between the higher noise emissions of Portland Cement Concrete (PCC) and lower emissions of Dense Grade Asphalt Concrete (DGAC). The purpose of this paper is to illustrate some curious characteristics of "average" pavement as it is employed in the TNM. Among these characteristics are what appear to be different methods for averaging the noise emissions for various vehicle types, such as automobiles, medium trucks, and heavy trucks. The inquiry concludes with an attempt to clarify exactly what constitutes an "average" when it comes to pavement noise emissions..

The overall noise level measured from chiller units is controlled by primarily tonal noises from (1) the fans, (2) the compressors, and (3) the associated pipework. Three large chiller units were measured using AHRI 370 methodology to quantify the overall sound level spectra and A-weighted sound level from different chiller units in a range of environmental conditions. Whilst this method can identify a general area of tonal emission to within a couple of meters across a unit’s surface that is emitting discrete tonal noises, the method is limited when there are multiple potential tonal sources. Sound intensity imagery was used on two units to quantify the overall sound power emanating from the source, but also to offer a more advanced method of localizing the source of discrete tones to aid in the application of mitigation treatments. Results presented include visually displaying and quantifying the location of noise emission from fan blade pass frequencies and associated harmonics, localization of problematic tones emanating from individual pipework junctions and valves, and the reductions in sound power emissions achieved from lagging compressors and pipework.

In modern commercial office design, sustainable building codes and quality standards often demand certain levels of sound insulation to ensure sufficient speech privacy or freedom from distraction for the occupants. Missing from the minimum requirements of these documents, however, is guidance on eliminating flanking weaknesses that repeatedly and significantly degrade the experienced speech privacy. This paper presents case studies of common acoustical weaknesses found between closed offices and meeting rooms. Through the use of sound intensity measurements and acoustical imagery, the sound power of each weakness is calculated and shown relative to the sound power of the separating partition. By comparing these results to partitions without these weaknesses, the effective reduction in speech privacy is demonstrated using the ASTC, NIC, and SPC metrics. Weaknesses examined and ranked include, open ceiling plenums, lack of or ineffective door seals, door closure pressure, continuous door frames, façade mullions and transoms, interior windows and their frames, lack of acoustical sealant, uninterrupted gypsum on side walls, common door frames at the edges of partitions, modular and operable walls and their junctions, continuous heating elements, thin continuous floor toppings, and ventilation duct crosstalk.

Speech privacy is a principal research area in speech communication. The term "speech privacy" is generally interpreted a condition where speech cannot be readily understood by, but may be audible to, an unintended listener. The need to prevent sound from intruding into adjacent spaces in both closed and open-plan settings is a concern in various office buildings. Speech privacy is essentially a function of the signal-to-noise ratio, comprising the noise reduction between source and receiver positions, and the masking effective of background noise. Speech Privacy Class (SPC) is one of the commonly used metrics for speech privacy assessment in closed plan offices in North America. However, there is a reluctance to use SPC between closed rooms due to laborious testing requirements as per ASTM E2638; there is a supposed preference to use either Speech Privacy Potential (SPP) based on simpler NIC testing, or to use Articulation Index (AI) despite the AI being created solely for testing open-plan settings. The ASTM E2638-10 standard SPC testing procedure does not assume a diffuse field in the receiving space but rather evaluates the performance at each potential eavesdropping location on the basis that there may be an intentional listener. Thus, to better apply the SPC to unintended listening and speech privacy in typical commercial spaces, the goal is to compare the current methodology as per ASTM E2638-10 with alternative sampling methods considering the talker location and unintended listening positions outside the source room.

Many open-plan offices adopt an electronic sound masking system in order to reduce distraction from background noises, primarily intruding speech. Sound masking systems should uniformly generate a masking sound over the entire office area to homogenize the speech privacy whilst minimising occupant perception of the masking sound. This study evaluates the spatial uniformity of the masking sound field in an example open-plan office, where the masking system was set up to represent supposedly optimal installation conditions; 1-speaker zones, individually-calibration of each zone to match the specified curve precisely, and smaller zones than typically specified. Sound level measurements performed as per ASTM E1573-18 were made at each workstation, as well as every 0.6 m across the office, for a total of 117 measurements. Measurement results show that tolerance of ± 0.5 dB for the overall A-weighted level is only achievable at 61% of measurement locations, whilst ± 1 dB is achievable at 99% of locations. For one-third-octave band sound pressure levels between 250 Hz and 4 kHz, ± 2 dB is achieved only 55% of the time, and tolerance of ± 3.5 dB is required to achieve 95% compliance with the specified curve. By using calibrated computer simulations, the study also examined parameters that can influence spatial uniformity in open-plan offices. It was found that the number of sound masking loudspeakers, partition height, and the scattering and absorption coefficient of the ceiling all affect the uniformity of the masking sound. Speech intelligibility was assessed by calculating the Articulation Index (AI) to determine an acceptable tolerance for masking sound variation. Increasing the number of loudspeakers was the most effective way to improve the uniformity of the masking sound. The AI results suggest ± 2 dB, when including octave band sound pressure levels, is a minimum required tolerance for a sound masking sound field in an open office to provide AI values within ± 0.1 of the targeted value across the office area.

An electronic sound-masking system reduces workers' distractions in open-plan spaces by utilizing an artificial broadband sound. The artificial sound should raise a background noise level spectrum to the targeted masking sound level uniformly over the entire area.Uneven distribution of the masking sound levels can cause unnecessary loud background noise or inefficient sound masking performance at the same time and in different locations. The ASTM E 1573-18 standard provides a procedure to quantify the uniformity of the masking sound but does not specify any acceptable degree of uniformity. Thus, this study aims to investigate the uniformity of the masking sound field in an open-plan space under varying room acoustic conditions. The acoustic measurement was carried out in an open-plan office with a measurement grid of 0.6 m. The spatial variation of the sound pressure levels was calculated with the measured one-third-octave band SPLs from 250 Hz to 4 kHz. The study also employed computer-aided acoustic simulation to find key design parameters, impacting the uniformity of the masking sound. The results show that the number of loudspeakers, a partition height, scattering, and absorption coefficients can significantly influence the spatial uniformity and speech privacy within the space. Finally, the results proposed an acceptable variation of the masking sound field by examining the Articulation Index (AI) change in the space.

Fans are used in a lot of industrial processes and are sometimes a source of important noise for workers. The first aim of this study was to identify some problematic fans in Québec industries, for which the noise exposure exceeds the CSST (Comission de la santé et sécurité au travail) limit of 90 dBA for 8 h. We have focused on fans having a high tonal content, for which the Simple Silence technology can be applied, i.e., tonal fan noise control using obstructions in the flow. Two analytical models of the tonal noise radiated by these fans have been proposed: a free field model based on the Lowson model and an in-duct model based on the Goldstein model. The first free-field model has been applied to the control of the noise from a series of eight evaporator fans, having a strong blade passage frequency (BPF) tone at 90 Hz. These fans have been controlled in-situ, in a cold storage room, using trapezoidal obstructions in the downstream flow field of the fans. The second in-duct model has been applied to control the tonal noise from an in-duct air-extractor fan used in the underground gold mining galleries. Several obstructions have been tested in the upstream flow field.

Active Noise Control (ANC) has been studied in the 90s as an innovative way to reduce the noise in specific situations. Some applications are well known today and found commercial success such as noise-cancelling headphones. However, the use of ANC in industrial applications is more complex, thus being an uncommon solution in this field. The use of ANC for industrial stack noise is one of these applications. One of the first large-scale implementation has been set up at the end of the 90s. This system was a 10-Channel ANC system installed on a 1.8 m wide chimney to attenuate a 320 Hz pure tone. At that time an 8 dB noise reduction was achieved at error microphones. In 2011, it has been decided to upgrade the system with the latest generation of Digital Signal Processor (DSP) allowing a real-time optimization and a better tracking speed. This paper describes the overall system and the updated multi-channel controller developed for this application. It also presents the improvements, the achieved noise reduction and the associated environmental benefits.