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Using Tone Generators to compare various IEMS and headphones

post #1 of 2
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Hi everyone — Mike here from Ultimate Ears. As some of you may know, I write weekly educational articles and industry interviews for UE on their UE University site. I'm pasting in full the current article as it's the first part in a 4 part series dedicated to evaluating and comparing various in-ear monitors. I'm a firm believer in giving this community as much real information as possible because with that, you all are able to make the most informed decisions in order to find a CIEM that best suits your taste profile. And while the start of this article may be a tad basic for some of you, discussing frequency sensitivity is something that's truly important and which isn't mentioned enough in the community. 

 

This first article is about pure sounds and tones. The next article will be about overtones, harmonics, time-domain profiles and how all of this relates to a good or bad mix. And the final article will talk about ear training and frequency recognition. It is my hope and belief that when we combine all these topics, we will slightly change how we listen / judge / evaluate phones — or better put, we'll be able to better focus our energy and attention on the frequencies and parts of the mix that matter most to all of us. For you see, there is no one [absolute] perfect in-ear or headphone out there. But there is a perfect solution for you based on your particular desires. And having the terms and concepts of what to listen for down pat will help you find what's best for you. So with that — I hope that everyone finds this as endlessly fascinating as I do.

 

What’s the best way to test and compare in-ear monitors?

Great question! In order to properly answer it, let’s start from the very top and then drill down. Before we can talk about how to critically judge an earpiece (or any speaker for that matter) we need to really understand sound dynamics.

 

We know that sound is a mechanical wave that is an oscillation of pressure traveling through a medium. We know that the corresponding wavelengths vary in size — ranging from around 56 feet to less than .05 feet.  And we know that all sound waves travel at a constant speed of roughly 1125.29 feet per second. When you combine all these facts, the idea of frequency & pitch becomes less abstract. 

 

So let’s look at a concrete example. If I hit the middle A key on a piano, the mechanical energy of my finger hitting the ivory is transferred to a mallet. That mallet then hits a string and that string creates a vibration. The length and thickness of that particular string lends itself to generating waves that are 2.56 feet long (meaning that that’s the distance between the peak to trough of the oscillations.) So those waves moves through the air at about 1125.29 feet a second and they interact with my eardrum approximately 439.56 times in one second. That’s the frequency. Middle A vibrates about 440 times a second. Get it — 1125.29/2.56 = 439.56. The same holds true for everything. If I hit a big deep drum and make a sound wave that is 56.26 feet long, that becomes 20 Hz (1125.29/56.26 = 20.001) meaning that those waves only hit my eardrum 20 times per second. The more times that a wave interacts with your eardrum per second, the higher you perceive it to be in pitch. 

 

Humans can hear frequencies that fall between 20 Hz to 20,000 Hz. Although we do tend to hear certain frequencies more accurately while we perceive other frequencies to be louder or softer — even when all other factors are held constant.  We are least sensitive to perceiving the sub bass frequencies between 20-60 Hz. We can hear between 60-200 Hz fairly accurately and our ears are the most accurate between 300-2000 Hz with our truest perceptions being right around 1000 Hz. From there, our ears get very sensitive and actually amplify perceived volume levels from around 2000 - 6000 Hz. This is great for sensing direction and vocal recognition but it can be harsh in musical terms if dealing with a bad mix. And finally, sensitivity dips back down in the higher frequencies from 6000-20,000 Hz although there is a pronounced boost in the 12,000-13,000 Hz range. 

 

 

So what’s all of this have to do with evaluating in-ears? Everything. Since music is the countless combinations of instruments and tones and pitches and frequencies and timbres and overtones and harmonics — all interacting with your eardrum at various sensitivity levels combined with how you perceive sound, it is impossible to tease out all the factors. You have to decouple the information and just listen to pure tone frequencies if you really want to get under the hood and hear how your piece performs. It’s the only way to know what it can really handle. 

 

Download these tone generating apps now and start isolating individual frequencies. How does your favorite pair of headphones measure up? How did the manufacturer address the frequencies that you now know you’re less likely to hear? Are they boosted? Are they even present? And what about the high-mids where you’re naturally sensitive. Are the tones harsh or are they clear? 

 

I personally use Tone Explorer for iOS. It’s $1.99 and worth every penny. 

 

Tone Generator is free for iOS.

 

And here is a free web-based Tone Generator 

 

More information on hearing sensitivity can be found here.

 

And here is a great chart on wavelengths for all frequencies. 

 

Now that you’ve been able to isolate and evaluate individual pitches / frequencies, listen to a full song and apply what you heard and learned. Can you hear if anything is missing or not fully balanced?

 

I'd love to hear your thoughts! And if you enjoyed this, please read on to part II.

 

 


Edited by Mike Dias - 12/2/13 at 10:50am
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post #2 of 2

Subbed. Thank you very much for this consolidated wealth of information explained in a simple manner. Much appreciated!

:beerchug:

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