Here's some interesting information copied and pasted from another site, note as a rule of thumb the shorter the barrel the louder the report, and as mentioned home loaded ammunition will also have a significant bearing.
{The peak dB depends a whole lot more on barrel length than on caliber, and whether the barrel is fitted with a muzzle brake or not. That's why in terms of dB, handguns are as loud as (or sometimes louder than) rifles.}
FreeHearingTest.com - Gunfire Noise Levels
Table 1. SHOTGUN NOISE DATA (DECIBEL AVERAGES)
.410 Bore
28" barrel.............150dB
18" barrel.............156.30dB
12 Gauge
28" barrel...............151.50dB
26" barrel...............156.10dB
18" barrel..............161.50dB
Table 2. CENTERFIRE RIFLE DATA
.223, 55GR. Commercial load 18 _" barrel.....155.5dB
.243 in 22" barrel...........................155.9dB
.30-30 in 20" barrel.........................156.0dB
7mm Magnum in 20" barrel.....................157.5dB
.308 in 24" barrel...........................156.2dB
.30-06 in 24" barrel.........................158.5dB
.30-06 in 18 _" barrel.......................163.2dB
.375 — 18" barrel with muzzle brake...........170 dB
Table 3. CENTERFIRE PISTOL DATA
.25 ACP...........155.0 dB
.32 LONG..........152.4 dB
.32 ACP...........153.5 dB
.380..............157.7 dB
9mm...............159.8 dB
.38 S&W...........153.5 dB
.38 Spl...........156.3 dB
.357 Magnum.......164.3 dB
.41 Magnum........163.2 dB
.44 Spl...........155.9 dB
.45 ACP...........157.0 dB
.45 COLT..........154.7 dB.