The prior answer that says it depends a lot on the caliber and weapon host is the most correct one.
Some calibers and weapons are much louder than others. Others sound better to your ear.
With that said, to your question about a suppressing a gun, many of them are still loud and sound unmistakably like a gun anyway.
The suppressor just takes a lot of the "boomy" out of it.
My example that I think should be used is a car because most people are familiar with how they sound.
Which is especially true since car mufflers are essentially the same principle and designed by the same person as a firearm muffler/silencer.
You take the muffler off a car and it's going to be very loud.
You put a muffler on a car and it's going to be a lot more quiet. But you'll still hear the engine running from a long way off, you'll know it's a car running, and you'll especially hear it when the car is speeding toward you down the street.
Also, when shooting supersonic bullets (which is the most common and available type of ammo), they have a sonic crack downrange that a suppressor cannot and does not affect.
When the bullet surpasses the speed of sound--1100 feet per second as most bullets are, there will be a crack that sounds like a regular 22 rifle shot being fired. This is on top of the sound of the shot when you fired it, so essentially, there are actually two cracks that occur when a bullet is fired. Though your ear usually just picks that up and sounds like one loud noise rather than two, but supersonic crack is more pronounced when you use a suppressor. Either way, you're going to know that someone just shot a gun.
That much is true regardless of which rifle caliber you're shooting from the old 30-30 hunting rifles that have been around for 130 years to the newest super duper magnum hunting cartridges.
Maybe this chart will help answer some of your question.
Unsuppressed firearms are not hearing safe and over 150 decibels.
Even the best case scenario, the suppressor will reduce the sound to around 120-130 decibel area, which is about as loud as your lawnmower and noticeably louder than a car horn, which are usually ~110 decibels.
Suppressed gunshots are in the 120-130 ballpark, and often louder, depending on what gun and caliber you are shooting.