Voice intelligibility in a room with noise levels at 75 dB is none existent as shown by the chart to the left. At 65 dB and above there is a dramatic shift down. This studied in a living room and from a document published in the Archives of the Centre for Sensory Research, Vol. 2, Issue 1, 1995. Normal conversation occurs at about 50 dB.
Some of the items that increase the noise the most are a vacuum (70 dB), music (76 dB),television (70 dB) a food blender (88 dB) . All of these items can reduce sentence intelligibility.