The claim of the OP is not unreasonable for high-frequency noise because the aluminum could shield from external electromagnetic noise. This is especially the case if
(1) you are using less-than-ideal RCA/phono cables
(2) your equipment has inadequate common-mode rejection on balanced runs.
Aluminum is an excellent conductor. The property that matters with respect to blocking extraneous is the skin depth is the skin depth, which characterizes how far a signal penetrates into metal. This can be related to the absorption factor as roughly A = 8.7 (t/d) dB, where t is the thickness of the foil and d is the skin depth. Derivation here. The skin depth for various materials is here:
So, let's calculate: at 60 Hz, the most likely source of noise, (see red line in plot) the skin depth for aluminum is about 12 mm. Your aluminum foil is about 0.16mm. Because you have multiple independent layers, we don't add the thicknesses of each layer together, but multiply the final absorption of a single layer by the number of wraps.
So, attenuation at 60 Hz is: 0.16/12x8.7 dB = 0.1 dB/ wrap. At let's say five wraps, you have 0.5 dB of reduction -- this is not even perceptible to the human ear.
At higher frequencies, you could do better. At 10,000 Hz, skin depth is 0.85 mm. You thus have 0.16/0.85x8.7 dB = 1.6 dB/wrap. At five wraps, you have about 8 dB of reduction -- this is noticeable. So, if you have RF noise present in the audio band, your aluminum foil could help with high-frequency stuff.
Note, there is some additional shielding from the reflection effect that is independent of the thickness; I ignored that. Also, these calculations are in the limit where the conductor is a sheet, not a circle, and that might lead to a significant deviation from the results computed here. Nevertheless, this illustrates the point.
(1) you are using less-than-ideal RCA/phono cables
(2) your equipment has inadequate common-mode rejection on balanced runs.
Aluminum is an excellent conductor. The property that matters with respect to blocking extraneous is the skin depth is the skin depth, which characterizes how far a signal penetrates into metal. This can be related to the absorption factor as roughly A = 8.7 (t/d) dB, where t is the thickness of the foil and d is the skin depth. Derivation here. The skin depth for various materials is here:
So, let's calculate: at 60 Hz, the most likely source of noise, (see red line in plot) the skin depth for aluminum is about 12 mm. Your aluminum foil is about 0.16mm. Because you have multiple independent layers, we don't add the thicknesses of each layer together, but multiply the final absorption of a single layer by the number of wraps.
So, attenuation at 60 Hz is: 0.16/12x8.7 dB = 0.1 dB/ wrap. At let's say five wraps, you have 0.5 dB of reduction -- this is not even perceptible to the human ear.
At higher frequencies, you could do better. At 10,000 Hz, skin depth is 0.85 mm. You thus have 0.16/0.85x8.7 dB = 1.6 dB/wrap. At five wraps, you have about 8 dB of reduction -- this is noticeable. So, if you have RF noise present in the audio band, your aluminum foil could help with high-frequency stuff.
Note, there is some additional shielding from the reflection effect that is independent of the thickness; I ignored that. Also, these calculations are in the limit where the conductor is a sheet, not a circle, and that might lead to a significant deviation from the results computed here. Nevertheless, this illustrates the point.
