Wire Loop And Amplifier Solve Audio Problem For The Hearing Impaired

January 29, 2020 by Dan Maloney 21 Comments

Imagine being asked to provide sound reinforcement for a meeting that occurs in a large room, where anyone can be the speaker, and in a situation where microphones would hinder the flow of the meeting. Throw in a couple of attendees who have hearing disabilities, and you’ve got quite a challenge to make sure everyone gets heard.

Such a situation faced [David Schneider] at his Quaker meetinghouse, which he ended up solving with this home-brew audio induction loop system. The worship style of conservative sects of the Religious Society of Friends, as the Quakers are formally known, is “silent worship”, where congregants sit together in silence until someone feels moved to share something. Anyone can speak at any time from anywhere in the room, leading to the audio problem.

Rooms mics and a low power FM transmitter didn’t work because those using radio as aids to hearing the service felt awkward, so [David] decided to take advantage of a feature in the hearing aids worn by some members: telecoils. These are inductive receivers built into some hearing aids to send sound directly to them using magnetic fields generated by a loop in the listening area. [David]’s loop ended up being 240 meters of 20-gauge copper wire in the attic above the meeting room. The impedance ended up close to 8 ohms, perfect for feeding directly from the speaker terminals of an old stereo amplifier. Pumping 160 Watts into the coil allows the hearing-aid wearers below hear the service now.

There’s still work to be done on the input side to improve audio quality, but [David]’s solution is elegant in that it helps those who need it most using technology they already have. And perhaps those who need but don’t yet have hearing aids can roll their own.

THAT Preamp

January 25, 2020 by Al Williams 2 Comments

It is easy to cobble together projects these days. ICs make it simple and microcontrollers even easier. However, we always respect a project that really goes from concept to finished product and that’s what we liked about [Curt Yengst’s] “THAT” Thing microphone preamp.

In part 1 of his post about it, he talks about the basic ideas including the chips from THAT — a small but high-end audio chipmaker — he uses. The first chip is a low-noise audio preamp and the other is a balanced line driver.

In part 2, we get to see [Curt] go from breadboard testing to PCB fabrication all the way to the finished rack-mounted device with a good looking front panel. It worked, but like all designers, [Curt] was already thinking about the next version.

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Ted The Talking Toaster

December 23, 2019 by Sharon Lin 9 Comments

The team behind [8 Bits and a Byte] have built a talking toaster. More accurately, they retrofitted their existing toaster with some hardware components to make it appear to talk and get angry at its users. While the actual toaster functionality isn’t necessary for the build, it certainly allows the project to have a more whimsical vibe.

The project uses a Raspberry Pi 3 and a Google AIY kit, consisting of a HAT, microphone, and speaker. Servos control the movement of the toaster’s eyebrows with the help of the HAT. Some decorative materials in the form of googly eyes and pipe cleaners help bring other features of the talking toaster to life.

The control flow for the chatbot makes use of Google’s speech-to-text for picking up text from audio input, the Dialogflow API to match intent, and Text-to-Speech to pipeline possible answer back to the Raspberry Pi to play over a speaker. They also used Remo.tv to broadcast live updates from the toaster to anyone on an online feed, allowing users in a chatroom to talk directly to Ted.

While Ted’s communications may be quite limited, there’s certainly no limit to the number of interactions he’ll be having online now!

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Paper Cup Mic Is Fun And Functional

March 2, 2019 by Lewin Day 6 Comments

Any studio operator worth their Protools subscription will have a wide array of microphones to cover any conceivable situation. SM57s to cover guitar cabs, fancy gilded ribbon mics for vocal takes, and a variety of condensers to round out the selection. That’s all well and good for high-fidelity recording, but what if you want to go the other way? [LeoMakes] has just the thing, with his sub-$10 paper cup mic.

The basic concept is that of a dynamic microphone. A paper cup is attached to a taut string, upon which a magnet is affixed. Sound waves hitting the paper cup cause the string, and thus the magnet, to vibrate. The magnet is located within a coil, created from thin insulated wire wrapped around an old solder spool. This induces a current, creating the audio signal.

Results are as lo-fi as you’d expect, with the exact character of the sound changing depending on the tension of the string and the exact materials used. It’s a fun project that can be tackled with cheap materials, and there’s scope to create all manner of wacky mics by varying the parameters of the build. If you’re doing this more than once, however, you might want some help winding the coils — let this project be an inspiration. Video after the break.

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Love Songs To The Microphone

February 12, 2019 by Al Williams 3 Comments

A biographer of Frank Sinatra once commented that for singers like Sinatra, their instrument is the microphone. We tend to think of microphones as ideal transducers, picking up sound faithfully. But like most electronic components, microphones are imperfect. They have a varying frequency response. They pick up popping noises when we say words like “popcorn” that are normally lost to someone listening live.

[Cheddar] has an interesting video (see below) that covers how performers like Sinatra, Bing Crosby, and Billie Holiday learned to use the microphone to their advantage. They suggest that the microphone changed the way humans sing, and they are right.

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Build Your Own Anechoic Chamber

December 14, 2018 by Bryan Cockfield 16 Comments

For professional-level sound recording, you’ll need professional-level equipment. Microphones and mixing gear are the obvious necessities, as well as a good computer with the right software on it. But once you have those things covered, you’ll also need a place to record. Without a good acoustic space, you’ll have all kinds of reflections and artefacts in your sound recordings, and if you can’t rent a studio you can always build your anechoic chamber.

While it is possible to carpet the walls of a room or randomly glue egg crate foam to your walls, [Tech Ingredients] tests some homemade panels of various shapes, sizes, and materials against commercially available solutions. To do this he uses a special enclosed speaker pointed at the material, and a microphone to measure the sound reflections. The tests show promising results for the homemade acoustic-absorbing panels, at a fraction of the cost of ready-made panels.

From there, we are shown how to make and assemble these panels in order to get the best performance from them. When dealing with acoustics, even the glue used to hold everything together can change the properties of the materials. We also see a few other cost saving methods in construction that can help when building the panels themselves as well. And, while this build focuses on acoustic anechoic chambers, don’t forget that there are anechoic chambers for electromagnetic radiation that use the same principles as well.

Thanks to [jafinch78] for the tip!

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High-End Headphones Get Flexible Boom Upgrade

December 4, 2018 by Tom Nardi 8 Comments

It seems a reasonable assumption that anyone who’d be willing to spend a few hundred dollars on a pair of headphones is probably the type of person who has a passion for high quality audio. That, or they work for the government. We’re fairly sure [Daniel Harari] falls into that former category though, given how much thought he gave to adding a decent microphone to his Sennheiser HD650 headphones.

Not happy with the results he got from microphones clipped to his shirt or mounted on a stand, [Daniel] realized what he really wanted was a sensitive boom microphone. This would be close enough to his mouth that it wouldn’t pick up stray noises, but at the same time not obstruct his field of view or otherwise get in the way.

He found a few options on the market which would allow him to mount a boom microphone to his HD650’s, but he didn’t want to stick anything to them and risk scratching the finish so those weren’t really an option. [Daniel] decided to go the DIY route, and eventually settled on a microphone that would mount to the headphone’s existing connector which plugs in at the bottom of the cup.

To make his mount, he 3D printed a two piece clamp that could be screwed together and securely attach to the connector without making any permanent changes. Once he had that base component printed, he salvaged the flexible metallic neck from a cheap USB light and used that to hold the female 3.5mm connector. Into that he’s plugged in a small commercially available microphone that is usually used on voice recorders, which [Daniel] said sounds much better than even the larger mics he had tested.

Finally, he used Sugru to encapsulate the wires and create a flexible strain relief. The whole assembly is very light, easily movable, and perhaps most importantly, didn’t require any modifications or damage to a pair of headphones which have a retail price that could double as a car payment.

It’s been a few years since we’ve seen anyone brave enough to hack their pricey Sennheiser headphones. But in the past we covered a modification which gave them an infusion of Bluetooth and even one that reversed a sneaky manufacturer hardware limitation.