Background
Anderson Acoustics was appointed by Fleet Architects to provide acoustic advice for a new gym within Soho House in Brighton. The gym occupies a ground-floor unit that shares its floor slab with the ceiling of the SeaLife Centre directly below. This arrangement placed particular importance on controlling impact noise and low-frequency structure-borne transmission from gym activity into the space beneath.
Our involvement ran across two stages, starting with an acoustic design assessment during the design of the fit-out and followed by commissioning and validation testing once the floors had been installed. The aim throughout was to confirm which floor constructions were suitable for commercial gym use above an occupied, and unusually sensitive, neighbouring space.
The Challenge
Dropped weights generate high-energy impacts that can travel through a building’s structure and re-radiate as low-frequency noise in the rooms below. Here the receiving space was not a typical commercial unit but the SeaLife Centre, an occupied visitor attraction housing live aquatic life.
This introduced two linked requirements. The first was the familiar one, keeping impact and structure-borne noise within levels appropriate for a neighbouring commercial occupancy. The second was less common. During the design survey, a SeaLife Centre representative observed that some aquatic life reacted to certain weight drops even when those drops were inaudible to our team and below the threshold of our instruments.
Any recommended floor therefore had to satisfy both a human response criterion and the observed response of the aquatic life.
Our Approach
During the design stage, we visited the site to test the existing structure and a range of proposed floor constructions. Airborne sound insulation testing showed that noise transfer through the separating floor was not a risk. The test signal was inaudible in the SeaLife Centre, masked by the good insulation of the slab and the high ambient noise from the centre’s plant and life-support systems.
We then assessed impact-induced re-radiated noise, replicating worst-case gym activity with a 35 kg dumbbell and a 20 kg kettlebell dropped from 0.5 m, and a 10 kg slam ball thrown from shoulder height, along with running on the spot to represent treadmill use. Weight drops were carried out over eight floor build-ups supplied by the flooring manufacturers, with noise and vibration measured in the SeaLife Centre directly below.
Measurements were assessed against the G-curve criteria in the Association of Noise Consultants (ANC) Gym Acoustics Guidance. Because the SeaLife Centre’s ambient noise influenced all measurements from 100 Hz upwards, the assessment concentrated on sound energy at and below 80 Hz, where impact-induced re-radiated noise is most relevant.
The Solution
The design-stage testing allowed the performance of each floor construction to be compared directly against the G35–G50 criteria and against the observed response of the aquatic life. This gave the design team clear, evidence-based recommendations.
A resiliently isolated build-up would meet the human response criterion in free-weights areas, and a higher-specification isolated build-up would be needed where the aquatic life response also had to be satisfied. Cardio activity was inaudible and carried no measurable risk, so any floor finish was suitable in those areas.
Once the selected floors had been installed, we returned during the final stages of the fit-out to carry out commissioning and validation testing. Weight drops were repeated across the constructed build-ups, including configurations with and without a loose 70 mm rubber top layer, so that the installed performance could be confirmed rather than assumed. A SeaLife Centre representative again carried out a visual inspection of the aquatic life during testing.
The Outcome
The validation testing confirmed how each installed construction performed. The more heavily isolated build-ups met the lower G35 criterion, with low-frequency noise levels falling in line with the existing ambient conditions in the SeaLife Centre. For these floors, the weight drops were inaudible on site and no response was observed from the aquatic life.
Some lighter constructions met the higher G50 criterion, and the testing identified where a particular build-up produced a response from the aquatic life despite the drops being inaudible and unmeasured, allowing that construction to be avoided in the relevant areas. No discernible vibration was felt or measured on any build-up.
The result was clear, site-specific confirmation of which floors were suitable for each part of the gym. This allowed the project team to make informed decisions on layout and operation with confidence, and without applying unnecessary constraints to the facility.
Conclusion
This project shows the value of carrying acoustic input through from design into commissioning where a gym forms part of a mixed-use building. By testing at the design stage, focusing on low-frequency impact noise, and validating the installed floors against recognised criteria, we provided objective assurance of acoustic performance and accounted for an unusually sensitive neighbouring occupancy, supporting the successful integration of a commercial gym above the SeaLife Centre.
Project Progress
The new gym opened in November 2023.
