Interesting... My experience does not include a bike shop. But it does include lots of chain drives under power. The rollers hitting the sprocket make a similar noise.
My bike experience is all shade tree except for 4 years in a real old fashioned "service" station where we fixed kid's bike tires for free and the kids knew it. I started the "bike service" when a kid filled his own tire like he saw us fill car tires and blew it up. The boss liked the idea of always filling them ourselves and/or with supervision so it became policy. He was an old softie and did not want to see a kid hurt. You would be surprised how many $ from regular customers that saw us fixing bikes flowed into the patch fund. We were sort of a bike "teaching hospital". The kids could watch us repair their tires and we always explained every move we made and why. Once they had seen it done a time or two they got to help... We also made adjustments and lubrication. The bike shop down the street about 5 blocks probably hated us but they charged the little kids just for looking at a bike. Parents would come in and have their cars serviced or filled and thank us. It was good advertising on our part.