Speech Privacy in the Workplace

The lack of speech privacy between adjacent areas is an all too common complaint in the modern work environment. Confidential conversations which should be private can be overheard with complete clarity. It is disturbing and can cause difficulty in terms of concentration, productivity for the person who is overhearing the conversation. Furthermore if one is aware that their conversation can be overheard it may well be a source of anxiety and concern.

Speech privacy is an essential component in so many aspects of life. We all have a need for and expect that our confidential conversation can be conducted in secure and private environment. This is the case in a doctor’s clinic, a solicitor’s office work, a meeting room etc. In fact anywhere where discussions of a sensitive nature are being conducted require appropriate levels speech privacy.

However total sound insulation between adjacent areas is not required. The fact that you are aware that a conversation is taking place within a room but you are only able to understand the odd word that is being said may well is acceptable. I would define this as the basic level of speech privacy.

The obvious problem, which is first identified, is the sound insulation performance of the partition structure between the adjacent areas. It could be a stud wall, a glazed wall, a door. More than likely the partition structure was selected for it sound insulation performance based upon data derived under test laboratory conditions. But lab performance figures require interpretation and can’t be taken directly at face value.

Our experience is that there is more than just sound insulation which affects speech privacy. Many more factors have to be considered, not least of all background noise. Many modern buildings with low noise air conditioning systems and external façade build-ups can result in very quiet conditions inside a building. This sounds like a contradiction in terms but too little noise can cause as many problems as too much noise.

There is a general speech privacy guideline which takes into account both the level of background noise and the sound insulation of a given partition. Table 1 below gives a summary of this method.

Privacy Rating Condition Speech Privacy
High Loud/raised voices are barely audible and are unintelligible 85
Good Normal level voices are just audible with raised voices
mostly unintelligible 75
Basic Normal level speech can be overheard some of the time
with raised voices clearly understood 65
Poor Normal level speech clearly overheard most of the time <65

Table 1. Speech Privacy Guidance Calculation

The speech privacy figure is derived from the addition of the partition structure sound insulation performance, Dw dB and the level of background noise. So to achieve speech privacy figure of 85 the calculation is as follows;

Dw 40dB + Background Noise Level 45dB = 85

In theory it looks simple but in reality it is difficult to achieve, especially in relation to adjacent areas. Therefore it’s never too early to get an acoustic specialist on board.

Jim Dunne is a senior acoustician with over 30 years’ experience in the field of acoustics and noise control.

For an indepth review of your workplace acoustic issues please contact us.