4 or 5 rooms. 4 rooms seem to benefit from having the 5 room units in between 4 rooms and the road, but noise might be coming from the whole stretch of roads. Any idea where is the main source of noise from? Nearer the junction or evenly spread out?
My experience on a 39 level unit of block 79 in Toa Payoh. Whenever there are activities in front of Library, the words from DJ and singers can be heard clearly (i.e. can understand). I guess sounds travel and also reflect. Probably at high levels, the lower decibel sounds can't be heard and therefore the only louder ones are heard. When the louder ones are speech/singing, one may still appreciate, but when the louder sounds are not noise, then one perceived that they can the noise is worse because the contrast is greater without the weaker background noise.