Everyone, welcome back to explain like a five weekly podcast where we take the questions you always want to ask and explain them in a way that is easy to understand You're your host and Tim. Hey, everyone's Kevin So Kevin have you heard about the new AirPods the AirPod pros? Yeah, I heard they're pretty cool Apparently they have noise canceling noise canceling is definitely a pro feature it is So that's what today's podcast is all about noise canceling now the first question is some headphones say their noise Isolating and others say noise canceling so is there a difference? What is the difference?
Yes? There's actually a pretty big difference. So let's start with noise isolating when people say something is noise isolating They're kind of like earplugs that have a ear bud in them. They block the outside noise by providing a noise reducing barrier Okay, right and something called this passive noise control Which is basically trying to reduce outside sound via noise isolate materials like insulation sound absorbing tiles a muffler rather than using a power source to actively Noise cancel noise canceling is very different They essentially listen to the ambient noise in outside world and produce an opposite sound wave to blank out Bell want to sound this is also called active noise canceling or ANC.
Okay, so we should explain how this works Yeah, so active noise control or active noise reduction is basically the method for reducing unwanted sound by the addition You actually created a whole another sound of a second sound specifically designed to cancel the first one. Does that make sense? Well, let's try a metaphor that five-year-old is that okay? Let's let's try it like this even do this with your five-year-old fill your bathtub with water, right?
And then drop two rocks into the tub one at each end of the bathtub Okay, so each will create a wave right and the waves will collide in the middle And you'll see a spot where the water seems very calm because the waves are basically canceling each other out, okay? Noise canceling headphones produces negative wave by listening to the outside noise and producing the opposite wave to cancel out the way of just like No, in the water. Actually analogy. So why do noise canceling headphones?
Why are they more effective with the low pitch sounds and not so effective when canceling out high pitch sounds? Yeah, yeah It's really interesting actually So like I said the way noise canceling works is that there's a microphone that has to pick up the no outside noise And then a speaker to produce the noise basically phase shifted 180 degrees to the opposite, right? However, the microphone the microphone can only pick up the noise as it's passing by and there's a very small delay before It can generate the phase shifted sound the cancellation sound right? That means you kind of have to guess what the future will hold in some sense and high frequency waves embed actually more information and shift more often Meaning it's a lot harder to make guesses about them compared to low frequency waves I see high frequencies are hard to predict and so hardly figure out.
Yeah Isn't there a difference also in the way that high frequency low frequency waves reflect? Yes, that's it So low frequencies are more spatially uniform again due to their longer wavelength and they travel through most materials without reflection And reflected waves interfere on a much larger scale than out of your head or ear It's not just reflection but also diffraction Low frequency waves have better diffraction This low frequency sound means longer wavelengths and longer waves bend more easily around obstacles and more ways to reach your destination So if you ever listen to a high frequency sound you know that even moving your head even a few millimeters can change the intensity due to the wave effects I see even low frequency sounds saying they sound the same from multiple spots in a room say multiple directions. Mm-hmm Yeah, so that's why a subwoofer essentially be anywhere in your room. That's right You know your ear gets no directional information by moving around or reflections So using a microphone to pick up the sound is that inverter is a sense of ear is much less useful The sound at the microphone is not exactly the sound you hear inside the ear and even the sound created by the headphone is not predictable I would generate some noise instead of really canceling it perfectly So the lower frequencies transmit better and farther and more uniformly than high frequency waves so they are easier to cancel out There's also one more interesting tip it which is actually got to do with how we hear so the human ear is most sensitive to frequencies around To the 2.5 kilohertz, but when it comes to lower frequencies the ear is not the only thing receiving the sound Oh, what?
Yeah, I mean so your bones and organs can also feel the vibration vibrations of a low frequency sound You know imagine like some ultra heavy bass is known to even interfere with the working of the heart So a lot of you know songs have bass frequencies boosted since the ear is most sensitive to that to the 2.5 kilohertz Bear band the lower frequencies needs a little extra energy for their bass to be perceived adequately And what is perceived as adequate bass today is actually most definitely more powerful than adequate bass 50 years ago Makes sense some of our phones today have noise canceling features just invisibly built into their system, right? Yeah, our mobile phones do a lot of things So many modern phones use a multi microphone design to cancel out any ambient noise from the speech signal This ends up making your voice sound much clearer Software is amazing. It's used to subtract the sound capture the microphone placed furnace from the mouth from the microphone closest to the mouth Which produces a much clearer speech quality? So if I have a question that people sometimes ask is and I got this earlier this week actually from a friend If noise canceling headphones are emitting sounds to counter the outside noise why might it not be You can't fall to hearing even the sound waves have to be loud enough to match whatever's coming in from the outside You know even though they hear the castle noise Right, right, right.
That sounds like you're a core kind of like double amount of noise there which is here But that's not exactly how it works back to the it's basically like destructive interference So your ears will not get damaged because the way noise canceling headphones work is that they cancel the sound before it reaches your Eardrum So your ear drum basically just doesn't even get vibrated and you don't hear sound as there's no vibration There's no harm and of course in reality noise canceling headphones don't work quite that perfectly Which is one of the reasons that you don't use it to protect your hearing Actically noise canceling headphones are not safety gear right here in protection like that on a construction site uses the passive noise blocking Got it. Well now that I know that there's no health risk. I think I've got an excuse to go out and buy those AirPods So you think yeah, I'm sure it'll be a great Christmas better Did you learn something new if you did send us a tweet at ely5 the podcast send us requests for few dress zones or send us a thumbs up on Twitter as always a big thank you to the subreddit explain like I'm fine see you all next week