In an office, we have noise that takes many forms. We have the most obvious, which is speech. However, there are numerous other noise producing sources that must be considered. We have machine noise from office equipment and telephones. We also have the noise of air rushing through the HVAC system. We could have projector noise to deal with in the conference room. Can we hear the cars outside our office? All of those systems can produce large levels of ambient noise which is then the benchmark that vocals have to compete with. The only way to compete with this background noise is to increase the gain on the speech in the room or as my associate always says on the telephone, “please speak louder”. Lets approach this one noise level at a time.
We Must Have Numbers
First, and probably the most time consuming step is to figure out what are noise problem actually is. This is critical in all noise evaluation scenarios nor matter what the budget restriction are. If we can quantify the actual noise level that we are dealing with, we can choose the correct amount and type of materials that we need which will avoid trying certain materials by using just guesswork. We can accomplish this by measuring the sound pressure levels throughout the day in our office.
For illustration purposes, lets view our problem as an energy pressure issue. Lets go to Radio Shack and purchase a SPL meter. Take the meter, place it on the a-weighted scale, and set it on your desk. Adjust the dB dial to 60 and start from that point. Watch the meter as the day goes by and look for two types of numbers to use in our calculations. First, look at the average sound pressure level that is generated during the day when your door is closed and it is just you and your office. Make a note of this number. Make a note of the number when you are talking on the telephone. Do this throughout the day.
If the office next door is showing a video presentation and there is audio attached, measure those pressure levels. If the office down the hall is throwing a birthday party, measure how much energy is in your office when the party is going on. Measure the levels when the air conditioning is off and measure the levels when it comes on especially the ones that have large internal fans. Measure the levels when you have one person in it. Measure the levels when you have two or more people in your office at your next meeting.
What Do All These Numbers Mean
Once we have the sound pressure level in your office measurement that shows the quietest moments and then we have the measurement that shows the moments with the most noise, we can look at the lower figure as our “noise floor”. This is the number that we will subtract from the high number to determine what we are dealing with and this number will show us how much sound pressure we need to absorb with our soundproofing materials. This number will tell us what type of material to use and what its density requirements are. Mass cost money and we only want to use what we need to use, no more, no less, to solve the room’s noise issues.
What Do These Numbers Mean?
Normal speech in an office environment is around 65 – 75 dB. If we look at our numbers that we have gathered and look at the number when we had one person in our office speaking, that number should be around 70 dB. That is a typical number for all ambient or background noise coupled with speech. If we have a number of 75 – 80 dB when we have just one other person in the room having a normal business conversation, we probably need to focus on blocking some sound energy from getting into our room.
Sound or noise issues that come from outside our rooms and then enters our room must be dealt with using barrier technology or in simpler terms mass. As we said before, mass costs money and we need to know how much mass we need to solve how large of a noise issue we really have. If our lower number in our office through the day is 65 dB and then raise quickly such as when there is a video/audio presentation in the next room, we know this is a one time or in frequent occurrence that does not warrant using a permanent full time solution for.
In Part-II, we will examine how we take our numbers we have gathered and translate those numbers to an acoustical material list that will deal directly with the numbers. No guessing on how much and how thick. The only decision will be what color.