Does It have to be loud?

For dB meter.
I own a digital Radio Shack dB meter. I keep it set to "C" weighted.
I also have a smartphone app. Also set to 'C' weighted.  Comparing the two, they are very close all through the range.
(one additional problem with the RS meter is the range is 10dB, adjusted with a knob. So one has to know in advance approximately what range you are measuring, or all you get is 'high' or 'low'.
No such problem with the phone app.
The phone or meter are used at my usual seated listening position.
The difference from holding the meter or phone in my hand at a comfortable spot vs right at my ear is too small to bother about. (though for purists I would admit the ear position is about 1dB lower than just holding it (since it is another foot or so further back. But I prefer being able to SEE the meter while I am using it. LOL

The big plus with the phone app is it records the dB level over several minutes. That is something the RS meter cannot do.

Now neither one has been professionally calibrated. but are way way better than no meter...
As for "gimmicky phone app" I guess you never actually used one. No gimmicks, just a useful app. (I would say its usefulness may depend on the phone mic. But most ($800 or so) Smartphones have a decent mic.

@elizabeth

I have tried numerous phone apps with multiple phones and they all read about 6 to 8 db lower than my Extech meter. I’ve only encountered one app that allows a C-weighted measurement, but it doesn’t record peaks like the Extech. If you blow into the mic of a real meter you can easily register over 100db. Try doing it with a phone mic and you’ll max out around 90db. 

First of all, thanks all of you for your input. I do agree that it is more about dynamics rather that just loudness. Any continued SPL above 85 dba will result in hearing damage, so needless to say this is not recommended. My hearing –after 40 years running around on electricity power plants- is not very good anymore, Nevertheless, I’m certainly able to enjoy the music, and I love the dynamics. Unfortunately, not many systems are able to present the full dynamic range available. Most of the systems will run into distortion when playing 90-95 dba SPL at listening position.  Don’t be fooled, 95 dba is loud! Now, considering a background noise level of let’s say 40 dba, and a dynamic range of 50 db on a very good CD, your system must be able to produce undistorted SPL of 90 dba. That’s it. You may wish to have a bit headroom, but if your system plays SPL peaks up to 95 dba undistorted, you’re good. Believe me, not too many systems can. Other than that, I play music at a level which I believe would be natural. So if a singer would be standing in between the speakers, how loud could she/he possibly sing without amplification, that’s the norm for me. Of course, occasionally I do play louder, depending on the music. But hardly ever do I exceed the 90-95 dba peak SPL. (and yes, I measure with an Extech SPL meter, it does make a difference)

Many people are a tone of deafness that the reason they listen loudly
if these people consult an orl  surprise they don t hear middle and high frequency but especially grave