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The noise level of a bullet in flight is primarily due to the ballistic crack, which is the shock wave generated by a projectile traveling faster than the speed of sound. This shock wave cannot be reduced by a suppressor and is separate from the muzzle blast noise[1].

According to the measurements provided in one of the search results, the bullet flight noise for a .223 caliber round (which is essentially the same as 5.56mm) was measured at 148.5 dB when suppressed and 148.1 dB when unsuppressed[1]. These measurements were taken 55 yards (about 50 meters) downrange from the muzzle and 1 meter to the side of the bullet flight path.

Given that the query asks about the noise level at 130 meters downrange and only 1 centimeter from the bullet, we can make an educated estimate:

1. The distance downrange (130 meters vs 50 meters) likely won’t significantly affect the noise level, as the ballistic crack follows the bullet.

2. The proximity to the bullet (1 centimeter vs 1 meter) would likely increase the perceived noise level, as sound intensity decreases with distance.

Considering these factors, we can estimate that the noise level of a standard velocity 5.56mm bullet in flight, one centimeter from the bullet and 130 meters downrange from the rifle, would be approximately 150-155 dB.

It’s important to note that this level of noise is extremely loud and potentially dangerous. Exposure to noise levels above 140 dB can cause immediate and permanent hearing damage[2]. Therefore, appropriate hearing protection is crucial when in close proximity to gunfire or bullet flight paths.

Here’s why:

1. Sound levels above 140 dB can cause immediate and permanent damage to hearing[1][2]. At 150-155 dB, the intensity is even higher and more dangerous.

2. The proximity of just one centimeter from the ear would amplify the damaging effects, as sound intensity increases dramatically at very close distances.

3. Exposure to 150 dB of noise can cause immediate and permanent damage to the delicate structures of the inner ear, resulting in hearing loss and tinnitus[1].

4. At levels around 150 dB, the sound is powerful enough to rupture eardrums[3]. This kind of physical damage would likely lead to severe hearing impairment or deafness.

5. For context, a jet engine during takeoff is around 140 dB, and even that is considered loud enough to cause immediate and permanent damage[2][3]. The levels in question (150-155 dB) are significantly higher than this.

6. The threshold for pain is typically around 120-130 dB, and sounds at 150 dB and above are considered in the “painful and dangerous” category, requiring hearing protection or complete avoidance[4].

Given these factors, exposure to 150-155 dB of sound just one centimeter from the ear would almost certainly result in severe hearing damage, including a high likelihood of deafness. The damage would be immediate and irreversible, potentially causing complete hearing loss in the exposed ear.

It’s crucial to note that such extreme noise levels should always be avoided, and proper hearing protection should be used in any situation where high noise levels are present.