5th Gen 4Runner brake boost - not making noise, should I be concerned?

I have a 2019 SR5 with under 11k miles that we just bought back in June of 2023. When we first got it, I noticed the hissing / air noise coming from the brake pedal every time I depressed it while driving. After researching, I found that it was the power brake booster and dismissed it. About a week ago I thought I was noticing very little sound coming from the brake petal, but ultimately dismissed it thinking I just couldn't hear it due to road noise, radio, etc. Well today I definitely noticed I'm not hearing it at all. I made sure to listen every time I braked and I'm definitely not hearing the quick little "pshh" that normally happens at the initial press. Should I be worried??? The truck still brakes fine. There's no warning lights on the dash. Brake fluid level looks normal.... I'm not sure what to think here. I keep finding conflicting information. Whenever I try to look online for this issue, I keep finding people asking what the noise is in the first place, nothing about why it stopped. I just know I'm going to feel silly explaining to a mechanic I'm bringing it in because it stopped making noise, when people are typically taking their car to the shop for unusual noises

 

You probably haven't gotten an answer because of perceived liability. Your best choice is to take it to a Toyota mechanic and explain your concerns. There are no silly questions when safety is concerned.

 

I noticed the noise after buying my 2019 new in 2019. Every now and then, I'd notice it again, and gradually got used to it, and didn't pay any attention anymore; lately, don't notice it at all. Of course, it's most likely due to my almost 70 year old ears not working like they used to. It doesn't concern me if mine brakes as it's supposed to.

 

I hear it sometimes and sometimes I don't.
As long as it brakes fine and there are no ABS related lights, you fine.