Me neither. But then it's not just 45 dB.
Your own TV should be about 60 dB at normal volume.
Yes, room modes can increase the sound pressure at a specific position. When two peaks of a sine wave meet, they act twice as strong as normal. And bass frequencies are particularly special anyway.
I gather that the neighbors are not very willing to compromise anymore? Have you ever invited the neighbor over when his speaker is on? Maybe then he’d realize it can no longer be considered just room volume?
It’s a difficult situation. Legally, you can only be sure with an expert opinion, but whether the expert will measure in your favor is unfortunately not certain.
We don’t have our TV particularly loud now. For example, children’s programs, where there is often little talking when we watch with the little one. And whenever not much “happens” on TV, you just hear the bass thumping.
Whether they are still willing to compromise, I don’t know. We have children the same age. The two can play nicely together, we have good conversations. We have also talked a few times about the music—and messaged 1-2 times on WhatsApp. I once sent a message asking if they could turn it off when they are no longer outside because we wanted to watch TV. No reply, but they turned it off then.
In face-to-face conversations, I might be too timid. I told them that the sound echoes extremely in our place, especially the bass. He then said something like “that’s strange, we don’t hear anything from you,” and I just thought, “no wonder, we don’t make noise,” but I didn’t say it. I’ve always tried to hint at it gently, but he eventually said “well, it’s just room volume, you have to put up with it, I should at least be able to hear it while I’m working,” and then I never know what to say. I don’t want to have trouble with them, but I also can’t use my garden like this.
If it happens again next Sunday, we’re thinking of going over and politely asking if they could turn it off, because we want to sit outside and it annoys us a lot.
I always approach them a bit gently. I don’t know if you know people like this—I don’t know much about them, but from little small talk, I always hear the same pattern: They have stress with their (ex-) employer, court cases, previous trouble with neighbors, stress with childcare... it paints a picture that they somehow always feel “treated unfairly.” It reminds me a bit of the old man on the highway who hears on the radio “ghost driver on the A28,” and says “one? hundreds!”...
I just want to keep things low-key because I don’t want to immediately join the league of people who have trouble with them. :D But I also want to be able to be in the garden on Sundays.