Former Fed Chairman Paul Volcker says the ATM is the only useful financial innovation of the past few decades. He's only sort of joking.

In any case, ATMs are a constant point of contention. Paying up to $6 to gain access to $20 of my own money is a bit rich. JPMorgan Chase (NYSE: JPM), Bank of America (NYSE: BAC), Citigroup (NYSE: C), and Wells Fargo (NYSE: WFC) have all raised ATM fees over the past few years. Why? Because they can. Get used to it.

But here's the latest ATM rip-off, according to Humans Invent:

[A] daily sound that is not quite what it seems is the comforting whirr of the cash point. The assumption most people jump to is that the sound is produced by rollers delivering the notes to the collection slot. In fact, the sound is an entirely artificial addition to the process.

The noise is produced by a speaker and purely included in the transaction to reassure you that your money is on its way. Without the added noise, the ATM would be practically silent with its moving parts on the other side of a brick wall.

The claim brought a gaggle of naysayers questioning whether this is actually true. For their part, Humans Invent pointed to a more well-known source, the U.K.'s The Times, confirming that, yes, the ATM whirr is indeed simulated.

If it is true, I don't get the point. I'm not reassured when the ATM goes clickity-clack. I'm reassured when the money comes out. More notably, I'm reassured by the FDIC guarantee sticker on the bank's door.

Any Fool engineers who can set the record straight? Let us know in the comment section below.

Fool contributor Morgan Housel owns B of A preferred. Follow him on Twitter @TMFHousel. The Motley Fool owns shares of JPMorgan Chase. The Fool owns shares of and has created a ratio put spread position on Wells Fargo. The Fool owns shares of and has opened a short position on Bank of America. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.