Improving the Restaurant Acoustic Experience
I recently had the opportunity to eat out at two nice restaurants on back to back nights. I wasn’t at either venue to evaluate the acoustics of the room but due to the major differences of the two rooms I took note. The first restaurant was rather large with a high ceiling and very hard surfaces everywhere with about 50-75 patrons sitting at tables and at the bar. There was no music playing but only people having conversations and typical sounds coming from the open kitchen area. We had a very difficult time having a conversation at our table and it was rather stressful trying to tune out the perceived background noise and talking with a raised voice. The second venue had a lower ceiling with no noticeable treatments on the walls and also had about 50-75 patrons sitting at tables and the bar and a similar kitchen set up. It had background music playing. To my surprise we could all hear the conversation at our table and found the dining experience to be very enjoyable.
As background, I remember reading a ZAGAT survey several years ago that said the number two complaint from restaurant patrons was the noise level of the room and the inability to hear a conversation at the table, with the first complaint being poor service. Given that most people dine out to socialize, having the ability to talk to others without raising your voice can be very important for patrons. Of course having a venue that utilizes sound to create a sense of excitement can also be important along with the room aesthetics, great service and great food.
So why was one experience stressful and the other enjoyable?
Covering all of the factors that answer this question would require a rather long explanation. What I thought would be best to address is a simple answer followed by a simple checklist, assuming your goal is to improve the acoustics of your environment.
All rooms that are intended to include people speaking, music or mechanical devices such as HVAC or cooking equipment contain a level of sound energy. The total level of sound energy includes the ambient sound energy plus the sound energy from all sound sources in the room. For a typical restaurant let’s assume the ambient sound is the sound with the room empty, no patrons, no music, just HVAC and outside noise that makes its way inside. Sound energy is then added from sound sources in the kitchen, people speaking and possibly music playing. The sound from the added sources can be considered direct sound until the moment in time in which the sound from any source reflects off of a surface in the room at which time it is referred to as reverberant sound. The main reflecting surfaces are walls, ceilings, floor, tables, and bars. Depending on how much of the total sound energy these surfaces can absorb will determine how much reverberant sound energy will be put into the room. The sound energy that is absorbed is removed from the room and turned into heat energy.
The simplest way to think about the problem of not being able to hear your conversation with another person at your table is as follows. When you speak to someone at a close distance of approximately 3-4 ft away, the sound from your voice is direct sound energy arriving at the receiver’s ears. When the level of reverberant energy exceeds a certain level it will mask the direct sound received by your ears which will make conversation and speech intelligibility more difficult. If you then speak louder to overcome the masking noise, you place additional sound energy into the room which eventually reflects off of a surface and increases the reverberant sound energy even more. Conversations become difficult and stressful, thus potentially degrading your dining and socializing experience. I will leave further acoustic details to future blogs.
So as a venue owner what are a few simple things to consider if you are trying to improve the sound of your room?
Observation – simply listen to the sound in your room and observe your patrons. Do they appear to be shouting in order to have a conversation?
Perception – Ask your customers about how they perceive the sound of the room and their ability to have a conversation. Is it comfortable or uncomfortable?
Criteria – understand the expectations for how you want your room to sound. Do you want an environment that is very quiet and intimate but provides privacy of conversation at a table? Do you want to provide music as a source of sound, if so at what level and at what locations in the room? What age patrons are you accommodating, remember that hearing loss can affect the perception of sound by older patrons? How willing are you to balance the aesthetics of the room with adequate sound absorption?
Utilize acoustic engineering analysis - although there are many solutions for simply applying acoustic solutions (i.e. absorption panels) to your room, without an analysis of your environment and application of good acoustic engineering principles, there is a good chance you are spending money on solutions that provide little or no benefit to improve your customer’s experience.
Analysis to consider - When working with an acoustic engineer you will want to make sure these factors are being included in the analysis
What is the ambient noise level? – sound level with nothing going on in the room
What are all of the sound sources adding sound energy to the room and what is the estimate of their sound level, individually and in total?
What are the transmission paths of all of the sources… what direction are they going in?
What is the shape or geometry of the room and can it be changed? What are the natural frequency modes of the room? These are natural peaks and valleys of sound levels (pressure) of specific frequencies of sound that are dependent on the room dimensions. If the dimensions can’t be changed, these peaks and valleys of sound at certain frequencies are fixed in specific locations in the room.
What is the Reverberation Time of the room? This is the amount of time it takes for a sound to decay 60 dB (starting level to low level). This is an important measure and there are published times for certain types of rooms (library to concert halls).
What is the total sound absorption of the room? This can be calculated using surface areas and absorption factors of each surface taking into account what it is made of. It can also include the absorption contribution of chairs, tables, people etc. (This is an indicator of how much sound energy the room can get rid of).
What is the reverberation sound level, considering all sound sources, and how does it compare to the sound level of speech between two people at close distance at a table? What level of speech masking does it produce? Does it cause the level of speech to increase in order to make the conversation able to be heard? Is this increase stressful or make your patrons uncomfortable? Does it exceed the criteria defined for your venue?
After considering the above, it will be easier to review and discuss potential solutions to achieve the criteria for your venue. Of course aesthetics and costs will have to be considered.
Although this is just a short summary of things to consider in making sound an important part of your customer’s dining experience, I hope it helps you in making informed decisions and spending your dollars efficiently.
As a side note, much of this information can be applied to other venues such as churches and synagogues, which traditionally are not very good at speech intelligibility. More to follow in a future blog.
