The question of how loud a generator is can be difficult to answer definitively. Sound levels are subjective, varying from person to person. What may be loud to one individual may not be perceived as loud by another, and vice versa. An analogy to illustrate this point is that my wife may consider my snoring louder than I do.
Attempting to quantify loudness in terms of decibels at a certain distance may not provide a comprehensive understanding. While a generator may produce 65 decibels of noise at 25 feet, it's important to note that modern units are sound-dampened, and with the enclosure closed, it's possible to have a conversation within 25 feet of the generator. However, this measurement does not convey the frequency or tone of the motor noise. Despite being as loud as an air conditioning unit, the generator's sound resembles that of a lawnmower.
A more relatable explanation is that when the generator is running, it may sound similar to someone mowing your lawn. Whether this is considered loud is subjective and varies from person to person. However, many generator owners find that the noise becomes background noise, akin to the hum of an air conditioner, especially during power outages when having a generator provides peace of mind.
Concerns about bothering neighbors with generator noise are natural when purchasing a generator. However, in my 20 years of experience installing generators, I have received zero complaints from standby generator customers about neighbors being disturbed by the noise. Not a single one. While it's understandable to anticipate noise concerns, I have yet to encounter a customer who regretted their generator purchase due to noise levels.