Because we work in different ways now than we did in 1975? The work people do is also different. And, the people themselves have also changed. A person born in 1980s may be more used to 24/7 noise from tv and devices. A 30 year old worker in 1975 grew up in a quieter home.
> Plants in the traffic noise treatment group were exposed to 16 h of road traffic noise each day for a total of 15 days, while the control group was kept under complete silence. Traffic noise exposure led to significant decrease in growth indices of both plant species.
Human change does not require Darwinian selection. Look across cultures. That people might tolerate or be most comfortable in noisier environments could vary for non-heritable reasons. Some people like less stimulation, some more. Autism rates have changed faster than our genetics also.
That generalization certainly doesn't fit with this 1977 edition human. The loudest 24/7 thing in my house is the compressor on my fridge. Silence (and office doors) are priceless.
I don't think people and how they work are much different now than in 1975. I have no data, though. That would be an interesting study. Do you have data?
I do. The data would be computer sales to businesses. The data indicates computer use is now a regular part of many jobs, whereas very few jobs in 1970 involved working on a computer, based on computer sales data.
