I’ve thought about this quite a bit and really consider advertising to be a form of assault on attention. The presumption that companies are entitled to our attention without our consent feels like an attack on our own agency.

Before we get to banning advertising though we first need to figure out how to connect people to businesses that have goods and services they actually want to seek out. Word of mouth is great, but it’s insufficient. We need some sort of directory. The yellow pages were surprisingly functional, but some modern accessibility and ability to update info is needed. I think the 10,000 pound gorilla in this space is Google maps. However, alphabet is fundamentally an advertising company at this point and prioritizes selling ad placement over user experience. Could organic maps eventually serve as a searchable business directory? I’m not sure. I think any open source initiative would quickly be ruined if companies thought that rigging that system woild get them more customers.

Is a public option viable? I’m not sure. There’s a lot of equal access and gatekeeping concerns there. We shouldn’t allow obvious scams to be listed, but what’s the threshold and who makes that determination? Is someone’s Mary Kay mlm a legitimate business or scam? The potential for corruption is very high in an endeavor like this. Imagine if someone is buddies with an administrator and can get their competition completely delisted. Such an endeavor would likely face lots of litigation over claims of unfair treatment.

Many companies I think would be eager to stop paying for advertising if they had a means of connecting to customers that was effective and lower cost, but to achieve this, you’re literally trying to compete with the entirety of google/alphabet.

The link I included in my comment goes over driving one in recognizeable notes to play the nokia tune. It’s worth a read if this concept interests you.

https://www.labdarna.com/en/understanding-piezo-buzzers-how-they-work-and-how-to-use-them-in-electronics-projects

They use piezo buzzers which work differently to most speakers. I would guess that the units used in smoke alarms and microwaves generally have integrated drivers that only operate at a single frequency. However, it is possible to drive piezo discs at different frequencies. Their ouput will always approximate a sound square wave though, so don’t expect to be able to use them like a normal electrodynamic/ voice coil speaker to play arbitrary sounds.