- Studies of user requirements, site conditions, planning, design and cost
- Defining criteria and targets to comply with regulatory requirements and specific needs
- Preparation of general outline of requirements
- Design review
- Criteria and detailed design reports
- Modeling and calculations
- Site visit
- Pre-completion testing
Our engineers are suitably qualified under environmental guidance to carry out site assessments and provide advice on the maximization of acoustic and lighting credits :
- BBC Energy
ALTERNATIVE was established in 2010 by two partners: Alexis Tremeau and Thomas Argence. They are both consultant engineers and have a Master degree in Acoustics and Lighting Engineering. They have previous work experience in prestigious Parisian agencies as well as in international ones (London and Tokyo).
ALTERNATIVE has now a dynamic, committed team with a musical and scientific expertise dedicated a wide range of project types. Our role as consultants brings us to rely on a constant dialogue with architects, set designers, digital and audiovisual technologies specialists, designers and artists.MEMBERSHIP
IOA - Institute of Acoustics
IALD - International Association of Lighting Designer
Airborne sound insulation is used to assess noise level difference both between adjacent rooms within the building (e.g. between offices, flats and music studios) and from external noise sources (e.g. road, rail and airplane noise).
The sound insulation between two rooms separated by a partition depends on the sound transmitted through the partition itself (laboratory acoustic rating Rw for Europe or STC for United States) but also on various other settings :
- The sound transmitted via flanking paths (through facades, technical ceilings and floors)
- Receiving room volume and reverberation time
- And workmanship issues such as gaps not fully filled, partition/slab junction not sealed well, wall linings not staggered
Based on our calculations and building site experience, ALTERNATIVE works with the project team to develop
technical solutions ensuring sound insulation requirements are fulfilled.
- In-situ sound insulation rating : DnT,w (Europe) - FSTC (United States) - (dB)
- The higher is the value, the higher the sound insulation is
Impact noise due to footsteps, dropped objects, scraping furniture or jumping children, can be a noise issue in contiguous rooms if the floor impact sound insulation performance is not appropriate. Therefore, energy due to impacts is transmitted through solid paths and is radiated by walls and floor constructions into noise in adjacent spaces.
To solve the problem, it is necessary to specify a concrete screed, a timber floating floor or a soft floor (e.g. carpet). Based on our experience, we give recommendations to ensure the floor build-up is appropriate and proper details have been taken into account in the design (e.g. acoustic underlay not bridged by service or skirting).
Rain noise can also be an issue. Impact noise of rain on skylights or glazed roofs can be really problematic (especially in restaurants, office spaces and classrooms).
Roof build-ups have to be selected (acoustic laminated glass) so rain noise is controlled.
- L’nTw (dB) for impact noise and Ln,e,w (en dB) for rain noise : The lower the value, the higher is the noise attenuation
Floor finishes can often produce unpleasant loud noise and disturb work activities when walked on. This type of noise is heard in the same room (contrary to impact noise) and is referred to as walking noise.
Therefore, it is essential to have a specific care when selecting floor finishes.
- Walking noise index Ln,e,w (dB) : The lower the value, the lower is the noise in the room
Public spaces (e.g. halls, restaurants, swimming pools, stadiums), working areas (e.g. offices, meeting rooms, open plan offices, classrooms), or auditoria (multi-purpose hall, concert halls, theatres), should be designed so reverberation is controlled. Absorptive materials and scattering elements can be used in order to do so.
Consequently, our role is to work together with the architect to select the adequate materials and define their integration in the space at the earliest stage in the project.
Key factors such as room volume and shape are aspects that have to be taken into consideration to avoid echoes (study of room dimension ratios, parallel surfaces) and uneven spectral responses (stationary waves, nodal modes).
- Reverberation time RT (seconds, s) : the lower the value, the driest is the room. The higher the value, the more reverberant is the room
- Attenuation by doubling distances A (decibel, dB) for big volumes as exhibit spaces or industrial halls : The higher the value, the driest is the room
HVAC equipment such as air handling units (AHU), chillers, pumps, but also electrical gears such as transformers are potential noise sources that can disturb occupants in a building.
It is possible to distinguish two types of disturbances :
- Airborne noise levels due to HVAC units themselves (radiated sound from a AHU unit, high frequency noise from an electromagnetic ballast) or indirectly (ductwork regeneration noise)
- Structure-borne noise levels due to vibrations from HVAC equipments with rotating motors (Chillers, AHUs, Generators,…)
We assist HVAC engineers in the plant design and equipment specification to prevent high airborne noise levels. We also make sure plant rooms sound insulation (positioning and design) , ductwork attenuation (ductwork noise calculations, silencers design) and regenerated noise (e.g. coming from airflow through dampers and terminal grilles/diffuser) are controlled.
Structure-borne noise levels due to vibrations can be reduced with damping solutions to attenuate the energy transmitted from the equipment to the structure (anti-vibration mounts, padding).
- Sound pressure level LAeq and Leq (decibel, dB) : The higher the value, the noisiest it is in the room
Plant noise is a potential source of noise disturbance for the nearest premises (e.g. roof plant such as generators and AHUs).
Thus, it is necessary to prevent those noise issues by designing solutions to attenuate noise so the project complies with regulations and local authority requirements.
To prevent and solve this issue, we carry out noise and vibration measurements, impact studies and calculations of outdoor noise levels around the site in activity.
We also use 3D modeling for noise mapping purposes.
Therefore we design technical solutions taking into account architectural and technical issues as well as economic aspects in the project. We carry out a noise assessment to ensure noise from the project will not create a future problem. Technical solutions usually take the form of acoustic screens, acoustic casing and attenuators.
- Sound pressure level Leq and Leq (dB) : The higher the value, the higher is the noise nuisance
Construction often generates community noise/vibration complaints.
Therefore, measures should be taken during the construction phase to mitigate noise and vibration.
For instance, ALTERNATIVE can give you recommendations on :
- Schedule of noisy activities with restricted times
- Noise specifications on construction equipment
- Alternative constructions methods
- Design temporary noise barriers
In addition, continue noise and vibration monitoring can help to assess noise levels and identify noise sources on site. It can also be used to define action levels to evaluate and take action to reduce the noise and vibration activity. It also contributes greatly to initiate discussion and arrangements between the parties (e.g. contractor and local residents).
- Number and positioning
- Sound power level
- Directivity and orientation
- Accurate positioning of speakers
- Line-array enhancement
- Acoustic criteria mapping on the audience area