ACOUSTICS
an item of mechanical plant had been installed only about 100 metres away from residential housing. Here the background sound level was around 55 dB(A); hence to achieve 45 dB(A) from the equipment at a distance of 100 m would not have provided acceptable sound levels. It transpired that the sound level criterion provided by the council was, in fact, 45 dB(A) at 1 m. This was one of the situations where someone telephoned me to report that they had ‘a bit of a noise problem’. On arrival, I discovered that the equipment supplier had endeavoured to control the sound to meet the criterion by building the equipment out of 1
⁄4 ” plate,
instead of 12 gauge steel. This did not prove successful, since the fans were the main source of sound.
Health & safety and plant room surveys
Having undertaken numerous and extensive surveys of hospital plant rooms, boiler houses, and roof-located mechanical equipment, very rarely have I encountered items of equipment generating sound at greater than 85 dB(A) at 1 m, and generally, the overall levels do tend to be around 70 dB(A) where staff may be working. One of the main locations where sound levels are above 85 dB(A), however, is power generation rooms, and I have never come across one that did not have an ‘Ear Defenders to Be Worn’ notice on the plant room doors. In conclusion, instead of an acoustician wondering through the hospital or other healthcare facility focusing on all of the building services equipment with a sound level meter, estates and facilities staff should take note of any especially noisy locations, and direct the acoustician to those where sound levels are excessive, whatever the cause. The prevailing sound or vibration levels can then be measured, and, where considered necessary, mitigating acoustic measures suggested. This approach has the added advantage that a visiting acoustician, who will only be inside the hospital and the individual ‘spaces’ within it for a limited period, may miss intermittent sound and vibration sources. Some hospital plant rooms are, in my experience, huge, and acoustic surveys of them can take a significant amount of time.
Complaints of noise from neighbours
Complaints about noise from hospitals and other healthcare facility sites, for instance from neighbouring residents, do occur from time to time, but it can sometimes prove difficult to identify the source. The reason is that some of the larger hospitals, particularly, have numerous different sources of sound – ranging from generation plant, refrigeration plant,
38 Health Estate Journal January 2021 An example of the extent of plant often external to a sizeable building.
venting of fume chambers, and HVAC (heating, ventilation and air-conditioning) systems, to vehicular activity from visitors, deliveries, and ambulances. As a result, the whole hospital is one large source of sound, made up of copious different sound sources.
An added complication, of course – as already alluded to – is that some sources of sound and vibration are intermittent, and not heard when a sound survey is being undertaken.
Anomalies can also occur from time to time; for instance in one case people living in flats near a hospital complained that noise from the facility had increased over a recent period. Initially, nothing in the way of an additional noise source could be found that would have impacted significantly on the sound received at the flats. However, after making night-time visits to the location in an effort to measure, we discovered that the Accident & Emergency Department had been moved to another location, and that the sound of ambulances that used to travel to and from the A&E had consequently ceased. Somewhat ironically, the sound from the ambulances had previously masked the noise from all the other aforementioned sources of sound. In other instances, having established the primary sound source for the ‘excess’ noise being complained of, an acoustic engineer may deem the potential solution prohibitively expensive. In most cases, if the complexities of, and obstacles to, addressing the issue are clearly explained, then nearly all complainants understand that very little can be achieved. In smaller hospitals, meanwhile, sound issues can often be resolved via the application of suitable acoustic measures.
Noise on hospital sites
It is well recognised that significant sound levels can arise in and around hospital buildings. This is often due to contractors, facilities management, and other personnel, not fully realising how much noise they are creating. We have all experienced annoyance due to sound levels produced around our own dwellings, and some of us complain about this. Patients and staff in a hospital do not usually complain, and will often simply ‘put up’ with a noisy situation – the patients because they are unable to, or do not feel they can, and the staff because they are usually so busy.
In one instance, when I was on a hospital site in the early hours of a morning, and had been checking sound levels during the night, I heard horrendous rattling noises in the early morning which started and seemed to go on and on. On investigation it was found to be attributable to deliveries being made to the hospital, and to the noise from the vertical cage type trolleys being used, which ran on caster-type wheels. The noise from the trolleys travelling between the lorry and the storage location would have woken sick patients, who no doubt needed to rest. This was neither the level, nor the type of sound one requires, in the vicinity of a hospital. On becoming aware of the situation, the Facilities team had the trolleys’ casters replaced with rubber tyres.
External contractors In another scenario, an external contractor was working on removing part of the walls on a hospital building. These contractors were removing a section at the base of each wall, and then smashing
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