Les said, the better II – The blog of Charles Celeste Hutchins

But surely the face-eating leopards won’t eat my face!

Many people who have invested a lot of time and energy into corporate platforms don’t want to walk away from that, which is entirely understandable. And anyway, they muse, how bad could it possibly be?

Let’s look at some risks:

Radicalisation – but that’s fine because I’m immune to propaganda.

Um, maybe? Some people are more susceptible than others. However, people are on the platforms they’re on because of the “network effect”. You’re there because your contacts are there and your contacts are there because you are. Some of them are susceptible and by staying in propaganda-filled environments, you’re helping expose them.

You’re also exposing yourself and your contacts to greater risk of hate speech. Zuckerberg went to the inauguration, stood next to a guy who gave Hitler salutes, and is also doing his part for Trump by allowing greater hate speech. Sticks and stones may not break your bones or hurt your feelings, but it’s highly damaging to some people. And also changes the political discourse and will impact our rights. Again, you and your friends are holding each other hostage via the network effect.

Multiple studies have shown that boys are being groomed into extreme misogyny via algorithms on video-based social media. Again, the corporate platforms are a problem.

Whether or not you’re personally immune (you’re not, sorry), society as a whole certainly isn’t.

Non-state physical threat – I’ll be fine

In the US, it’s extremely clear that radicalised actors face a physical threat to minoritised groups. My own opinion is that migrants (and the children of migrants) who actually are in quite a lot of danger. Facebook has previously been a major platform for planning and coordination for at least one genocide.

Women and LGBT people are also at high risk of doxing, via Meta. “The Facebook platform makes doxing particularly easy and rewarding for doxers.” Facebook has also leaked personal information to people pretending to be police, as no warrant is required in emergency situations.

Maybe you’ll be fine, but some groups are in serious danger.

State-based threat – I’ll be fine!!

Americans generally don’t really have very many data rights. Europeans have many more, but Meta routinely ignores them (getting fines that would be massive for a less-profitable company). The problem is not just that they mishandled data, but they’ve been accused of collecting excessive data they had no right to and which users hadn’t and couldn’t consent to.

That data includes information like gender, race, sexuality, orientation, trans status, susceptibility to addiction – it’s far ranging. Indeed, Meta collects and utilises data about users likely race and other protected characteristics. Some of this data, say, identifying Hispanic Spanish-speakers, may be useful for Trump’s campaign promise of putting people into camps.

And, if a court orders Meta to share any of their collected data with the cops, they have to comply. Which is how they came to participate in helping prosecute abortion care.

If they stored less data, or kept messages encrypted, they would not have had access to this data to share. But instead, they also track as much information as possible from their own apps and from other, unrelated apps listed in your phone’s app store.

I searched my phone’s app store for “period tracker” and the top result leaks data to facebook. Apps with Facebook trackers collect “off meta activity” to use to show you adverts. Or to share with anyone who has a court order demanding they do so.

They also track your relationships on and offline, via apps, partly by tracking location.

WhatsApp’s message content are encrypted and thus not visible to the company, but they know who you message, how often, at what times, where you are when you send them. This is called metadata and in some ways it’s more valuable than the message contents. Not for prosecuting abortions as above, but for inferring relationships and life circumstances.

The sheer amount of surveillance available to state actors is dizzying. But you’ll be fine, right?

Oh wow, no, we need regulation, especially to protect kids!

It’s absolutely true that individual action is not going to put a stop to this, and larger, collectivised action is necessary. The GDPR in the EU is a great step, even if it took them a very long time to act and fines were small relative to Meta’s income.

The situations in the US and the UK, however, are a long way off from the EU. The UK is too small and isolated to act with any real teeth and the US is currently pro-abuse.

You may be thinking of some proposed legislation purported to benefit the online safety of kids. But those proposed laws were written by the companies they’re meant to legislate. They’re written in such a way that no social media site could possibly comply with them unless they have the resources of Meta. The version proposed in the UK would have outlawed Wikipedia. They’re meant to extend monopolies, not to protect kids.

Indeed, the language they use for marketing these ideas is the same language used by the governor of Florida while enacting rules against trans youth. “Letting kids be kids” means keeping them away from knowledge about trans lives, gay lives, protection against STIs, or any kind of sex or gender education. Enshrouding children with enforced innocence is compulsory cisgender heterosexuality. It is “anti woke” ignorance in which discrimination is tolerated by its antidotes are not.

The version of this just passed in Australia requires age verification for the entire country for many normal activities. This hampers anonymity, puts people subject to abuse at greater risk, and deprives kids of vital information.

We must stay and fight!

Karl Marx thought that the revolution would come when the workers seized the tools of production. Even now, people are clinging to Twitter – a site owned and controlled by somebody who Seig Heils – vowing to hold their ground.

But this isn’t like holding on to a piece of land against an advancing army. The oligarchs not only own the land, they own the physics. It’s like fighting G-d. They control who, if anyone, sees your posts and everything that you see. That is not at all like real life or even like ancient myth. G-d sometimes plunged people into darkness or plagued them with flies or even opened chasms beneath them, but everyone present was in the same reality, seeing the same things. That’s not true on a virtual platform.

Fox News used to run a show called Hannity and Colmes. Hannity was a tough, jockular bloke who was right wing. Colmes was a tame, soft-spoken liberal. They faced off each other to debate, except they didn’t. The terms, the framing, the guests, and everything about the show was meant to give right wing audiences an illusion of debate, but it was never a fair match. Even the settings of the microphones was such that the right wing voices were objectively louder than the liberals. If Colmes had been actually effective at countering right wing narratives and framing, he would have been fired.

Nobody is actually “staying and fighting” on Twitter. They’re just the loyal opposition. They’re a figleaf of balance where none exists. They’re being used and exploited and unlike Colmes, aren’t even getting anything in return. He got paid. Liberals on twitter are giving resources and cover to Musk.

Some of the corporate platforms may “feel” more balanced, but their owners are loyal to Trump and are quickly lining up. In the West, the workers did not ever end up seizing the factories they worked in. The means of production stayed in the hands of capital. But at least Marxists had a credible plan for how victory might have come about. There is no credible path wherein Facebook users seize Meta. There’s just not.

You Get a better world by building it.

Leftists talk about the “power of the people”. The people are building alternative platforms which are not under oligarch control and are structurally resistant to capture. That’s the way forward. Join a movement that will immediately (although individually) solve several of the problems listed above and which provides a route for the future.

A better world is possible and is much less far away than it seems.

But it does mean stopping giving all your data to Meta, Google, Apple, Amazon, and X.

Join the movement. Go to fedi.

But what about Bluesky?

This platform – invented by the guy who started Twitter, then refused to moderate it properly and eventually forced the sale to Musk after Musk wanted to back out- sorry, where was I?

Bluesky has a single point of failure. They could decide to sell it to Musk too. Or to Meta. Or to Google. Or to Amazon, or to whoever. It’s backed by capital, so it’s for sale.

To prevent this, there’s a group of people trying to build a “spare” server so Bluesky users can easily hop between them when the main Bluesky stops being in the fun early phases of trying to build up a user base and moves on phase 2 where it tryies to wring data and profit out of everyone. The people making the spare estimate that their server will cost $30 million USD and take three years to set up. That’s apparently not counting running costs after those three years are up. Which may be a moot point, as currently, this is also not technically possible. It requires the capital-backed team at Bluesky to build the tools to make this possible.

And if the hypothetical $30 million dollar spare server also gets caught up in US politics, what then? Do they need to raise another $30 million?

By contrast, a small mastodon (or other fediverse) server can go up in an afternoon and be run for a few dollars a month. Nobody quite knows how many are running right now- it’s in the thousands. Some only have one user. Some have hundreds.

The social media project with thousands of people working independently as part of a loose movement is harder to capture than a centralised, expensive project. It’s not just run by one or two teams. It’s not in one or two countries.

I know your friends are on Bluesky. . . . Like they are on facebook and were on twitter and were on myspace. . ..

Part of the reason people like the fediverse is that it’s really very easy to move between instances. If queer.party turns out too be too unserious, I can go to scholar.social and keep my contacts. I would argue that this is better than herding ourselves into yet another walled garden that cages us. To another billionaire who turns fascist.

You can be on many websites at a time and you don’t have to choose – it’s possible to have both kinds of account. I’m just kind of tired of being caught in traps again and again and again.

Get Away from Meta and X Now

We’ve all seen the pictures from Trump’s inauguration – Elon Musk, CEO of Twitter and Mark Zuckerberg, CEO of Facebook, WhatsApp and Instagram; stood in the front row. And of Musk giving a Nazi salute. The CEO of TikTok was not in those pictures, but he was also there. The collaboration has already started. Facebook has already helped arrest and prosecute people for abortion.

Ditch WhatsApp

Get Signal instead. I’m on there. Find me via my phone number or send me an email.

Ditch Insta

The hot new platform is PixelFed. You pick an “instance” to join and then can follow any other PixelFed user on any instance. I’m trying out Pix.lgbt, which is run by a trans woman.

Pixelfed is part of the fediverse. (keep reading for more)

Ditch Twitter (or Threads)

As in, actually delete your X account. Don’t just stop using it. You need to deactivate the account, wait 30 days and then demand that the data actually be deleted.

The popular replacement for twitter is Mastodon. But don’t just pick an instance at random, because they all have different moderation policies. For queers and allies, a good one is https://lgbt.io. If you’re a musician, you might enjoy https://sonomu.club/. If you’re Jewish (and get on well with liberal zionists), https://babka.social/. If you’re not sure, just do lgbt.io. It’s extremely easy to move your account between servers, so if you decide later that you should have been on a different server, you can move. However, your early experiences are going to make you feel happy or not, so do get a recommendation for an instance. The flagship one has moderation problems and puts many people off.

Mastodon is part of the fediverse. (keep reading for more)

Ditch Facebook

You could just join Mastodon, but for people who like nicely threaded replies and discussions where you can see who has replied to what, people like Misskey (or the million sub-variants of Misskey). I’m trying out https://blahaj.zone/ which is very queer friendly.

Misskey is part of the fediverse. (keep reading for more)

The fedi-what?

Mastodon, Pixelfed, Misskey and several other platforms all interoperate. If you join any Matsodon instance, you can follow anyone on any of them, on any instance. The differences between them are the interface, the moderation, and the community that is local to each instance. (Pixelfed, reasonably, only shows posts that contain pictures, so isn’t a good way to follow Mastodon users.)

In practice, this means that wherever you join, you can follow me: @celesteh@lgbt.io. (You can also follow this blog: @celesteh@www.celesteh.com )

This is important because it means that this network cannot just be purchased by Elon Musk, even if he buys this blog, he can’t buy every single Mastodon server. This network can never be fully captured by oligarchs.

Getting started

I just wrote a thing about how to sign up at another blog yesterday, so go read that.

Once you’re signed up, upload a profile image, fill out your bio and write a little #introduction post.

Then follow me. Send me a message if we know each other online or in real life.

Tell your friends where you’ve gone. And why. If you want to post this message to X or any Meta property, you’re going to need to be cryptic, because they will not let you link to their competitors in a post.

Octatonic Scales in SuperCollider

You can generate your own Octatonic scale in an arbitrary Equal Temperament using the following code.

Change octaveRatio to the ratio you’d like and steps to the number of steps. The Scale is saved to the global variable o;

(

var octaveRatio = 2, steps = 12;
var ratio, tuning_arr, tuning, octatonic_arr, octatonicScale, index;

ratio = octaveRatio.pow(steps.reciprocal);

tuning_arr = steps.collect({|i| ratio.pow(i).ratiomidi });
tuning = Tuning(tuning_arr, octaveRatio);

index = 0;
octatonic_arr =[];

{index < steps }.while({
	octatonic_arr = octatonic_arr.add(index);
	index = index+2;
	(index <= steps).if({
		octatonic_arr = octatonic_arr.add(index);
	});
	index = index + 1;
});


octatonicScale = Scale(octatonic_arr, tuning: tuning);

o = octatonicScale;
)

You can then use this in a Pbind by using \scale. For example:

(
Pbind(
	\scale, o,
	\degree, Prand((0..7), 7)
).play
)

Try out different Equal Temperaments

Note: Code for this post is available on github here.

Tuning scales is about ratios. We multiply the root frequency by a given ratio to get a note in the scale. In Equal Temperament, all ratios are equal, the 12th root of 2. Which is 2^1⁄12. We multiply a frequency by that to get the next frequency in the scale. When we’ve gone through all 12, we get the octave. (2^1⁄12)¹² = 2.

Let’s say we want the 3rd note in the chromatic scale. We have the root and multiply by the ratio for the second and then for the third. For the fourth, we do it three times. For the fifth, four times. Therefore, for any chromatic scale step 𝘯, we multiply the root by 2^{(𝘯-1)⁄12}

But, especially when we’re using computers, we can try out putting the notes in different places! What if we have 10 steps per octave? Then our ratio is Which is 2^1⁄10. The composer William Sethares has written music using 10 tone equal temperament and in other unusual tunings, which you can listen to on his web page.

We can even forego octaves entirely. The Bohlen-Pierce scale is based on divisions of 3, rather than 2. When people use equal temperament with that scale, they typically have 13 steps in the octave, which makes their ratio 3^1⁄13. The composer Elaine Walker is one of many who has written music using Bolhen Pierce and you can find examples on her website.

We can also try out different tunings ourselves! Below, you can try out different Equally Tempered scales. Change the steps value for the number of divisions you want. If you want to try out Bohlen-Pierce, change the octave ratio to 3. Or try whatever tickles your fancy.

Your tuning ratio is 2^1⁄12, which is equal to 1.0594630943592953

12tet’s ratio of 2^1⁄12 is equal to 1.0594630943592953

It can sometimes be difficult to hear the differences in pitches just going up and down a chromatic scale. Modes like major and minor are very strongly tied to a 12 note chromatic scale and it doesn't make sense to try to, say, play a 10 note major scale. However, the octatonic scale is a mode that can potentially work for any tuning. It alternates whole and half steps. Perhaps listening to the octatonic versions of your scale and 12tet will demonstrate the differences more clearly.

Or we can try a phrase by Debussy:

Plugins for music, equations, etc

In the hope of making my text here more accessible, I’ve installed a few new plugins. Rather than take screenshots of a notation program, to show notes, I’ve installed Music Sheet Viewer. This is supposed to support Plaine and Easie Code, which is meant to be a dead easy way to input a few lines of notes. However, I couldn’t get that to work, so I input the Plaine and Easy Code into a free online converter, which turns it to MusicXML. It supports this format without a hitch. I’m sure I’m doing something wrong and will be able to simplify this soon.

For maths formulas, I tried very many plugins. The one that finally worked was QuickLaTex. As the name implies, it uses LaTex syntax for layouts. I’m under the impression that this increases accessibility for screen reader viewers, although perhaps not as much as MathsML. I tried many plugins nad this is the only one I could get to work. Of course, MathML is in Jetpack, but so is a bunch of SEO garbage that I’d rather live without.

Finally, I’ve enabled the ability to upload SVGs. I used WPCode, which is a code snippet library. It added a function for SVGs. This was better than trying to do this by hand, especially as it worked the first time without breaking my site.

My next step is to write or deploy a little javascript toy to let people try out different equal temperaments.

Science of Sound Week 2

Frequency

Previously, we talked about wave length and frequency. We measure frequency in Herz, abbreviated as Hz. A 1Hz sine wave goes through a complete cycle one time per second. A 440Hz sound wave goes through a complete cycle 440 times per second. The frequency is the reciprocal of the duration. A single cycle of a 440 Hz sine wave is $\frac {1} {440}$ th of a second.

We also talked about the speed of sound, which is 340 m/s at 20 degrees celsius. If we have a 1 Hz wave, travelling at 340m/s, it takes one full second to get through the complete cycle. Which means that the front of the sound wave is 340 metres away from the back. The wavelength is 340 metres.

A 2 Hz sine wave also travels 340m/s. The time it takes to get through each cycle is half a second. In half a second, the front has travelled 170 metres, which is to say that’s the wave length.

A 10 Hz sine wave lasts $\frac{1}{10}$ th of a second, so the wave length is $\frac{340}{10}$ , which is to say 34 metres.

A 100 Hz sine wave is $\frac{340}{100} = 3.4$ metres. The octave higher, 200 Hz, is 1.7 metres. The wave length is the speed of sound ( $c$ in the formula) divided by the frequency. $\lambda = \frac{c}{f}$

Tuning

We mentioned 440 Hz in the first paragraph. If that sounds familiar, it’s because it’s also the frequency of most tuning forks. It’s the defined frequency for A.

MusicSheetViewerPlugin 4.1

We also know that if we double the frequency to 880, that’s also and A. Or if we halve it to 220.

MusicSheetViewerPlugin 4.1

110 Hz, 55 Hz and 27.5 Hz are also As. As we get lower the frequencies get closer together and as we get higher they’re farther apart. 7040 Hz and 14080 Hz are also As.

Figure 3: Diatonic scale notes graphed by frequency. The curve of the notes is exponential. By SharkD, Public domain, via Wikimedia Commons.

We know that all As are 440 multiplied or divided by a power of 2. We also know that doubling any frequency gives us an octave of that frequency. We can generalise from this to come up with a formula for a one note scale based on the octave. Where $f$ is frequency, $f \times x = 2f$ . It’s obvious here that x is 2.

What if we want a two note scale that uses Equal Temperament? This is a system where all the notes are equally distant from each other perceptually. We know that this has to be based on multiplication. We want an equal ratio between all the notes. Therefore to get from the bottom note to the next one, we need to multiply by some number x. And then to get from the middle note to the octave, we multiply by x again. $f \times x \times x = 2f$ We can simplify those two xs. $\therefore f \times x^2 = 2f$ And divide both sides by f. $\therefore x^2 = 2$ Solving for x: $\therefore x = \sqrt{2}$ . Our two note scale is 440, 622.25, 880. This is because $440 \times \sqrt{2} = 622.25$ and $622.25 \times \sqrt{2} = 880$

What about a three note scale? $f \times x \times x \times x = 2f$ Which means $\therefore x^3 = 2$ and so $\therefore x = \sqrt[3]{2}$ To work out this scale, $440 \times \sqrt[3]{2} = 554.37$ , $554.37 \times \sqrt[3]{2} = 698.46$ , and $698.46 \times \sqrt[3]{2} = 880$ .

If we want a 4 note scale, we can use $\sqrt[4]{2}$ or for a five note scale $\sqrt[5]{2}$ . But for a piano, we want 12 notes, including all the white and black keys.

Figure 4: A one octave keyboard by Lauri Kaila CC BY 3.0 https://creativecommons.org/licenses/by/3.0, via Wikimedia Commons

Therefore, the tuning used by the piano, called “12 Tone Equal Temperament” (or 12tet) uses $\sqrt[12]{2}$ .

We know that the frequencies are exponential, but perceptually, the difference between a C and and A is the same in any octave. Our scales and keyboards and the musical concept of pitch is linear. Every octave may double in frequency, but it’s always only 12 semitones.

Figure 5: “Logarithmic plot of frequency in hertz versus pitch of a chromatic scale starting on middle C.” via https://en.wikipedia.org/wiki/Musical_note. Image by Jono4174, public domain via Wikimedia Commons.

You now know enough to work out the frequency for every single note on the piano. (Or, you can look it up on wikipedia.) You can also work out the wavelength for every frequency on the keyboard. If the lowest note is A₀, the frequency is 27.5 Hz, so the wavelength $\lambda = \frac {340}{27.5} =$ 12.4 metres. And the highest note, C₈ is 4186 Hz, so $\lambda = \frac {340}{4186} =$ 0.081 metres. What a range! And that’s not even the highest note we can hear!

Going Further

Not all scales are based on octaves! The Bohlen-Pierce scale is based on multiplying frequencies by 3. How could you compute an equally tempered scale for Bohlen Pierce? If you wanted the scale steps to be roughly the same size as 12tet, how many scale steps would you use?

Waves

What if we want to graph the pressure changes in air made by somebody playing the flute? The graph might look a bit like this:

The vertical axis is pressure and the horizontal axis is time. We can see the pressure increase, decease and increase again. The idealised wave form shown here is a sine wave. This wave has exactly one frequency in it and is the simplest possible wave form.

If you generate a sine wave in your DAW and then zoom way in, you’ll see exactly the same shape, but in that case, the Y axis is how much the speaker cone will offset when we play back the sound. This makes sense. The speaker needs to push the air to make the sound wave. If we were looking at an analogue signal to the speaker via an oscilloscope, the Y axis would be the amount of voltage.

If the wave is taller, the speaker moves more air and the sound is louder. The height of the wave is the amplitude.

The height of the wave is labelled amplitude and the distance peak to peak is the wavelength. — Figure 2: Wave, wavelength and amplitude CC BY 3.0 <https://creativecommons.org/licenses/by/3.0>, via Wikimedia Commons

The distance from one peak to another, λ, is the wavelength. If the wavelength is shorter, the speaker cone moves faster. A faster movement and a shorter wavelength means a higher frequency.

We’ve measured from the peaks, but we could measure from any point along the curve, for instance, from the zero crossings, as long as the wave has been through a complete cycle.

Figure 3: Phase by Baskurtf at Turkish Wikipedia., CC BY-SA 2.5 https://creativecommons.org/licenses/by-sa/2.5, via Wikimedia Commons

If waves start at different points but have the same wavelength, we say they are the same frequency but have different phases. In figure 3, the red line starts at zero and is a sine wave. The blue line starts at 1 and is a cosine wave. They both are the same frequency.

We have the unit circle (with radius = 1) in green, placed at the origin at the bottom right.

In the middle of this circle, in yellow, is represented the angle theta (θ). This angle is the amount of counter-clockwise rotation around the circle starting from the right, on the x-axis, as illustrated. An exact copy of this little angle is shown at the top right, as a visual illustration of the definition of θ.

At this angle, and starting at the origin, a (faint) green line is traced outwards, radially. This line intersects the unit circle at a single point, which is the green point spinning around at a constant rate as the angle θ changes, also at a constant rate.

The vertical position of this point is projected straight (along the faint red line) onto the graph on the left of the circle. This results in the red point. The y-coordinate of this red point (the same as the y-coordinate of the green point) is the value of the sine function evaluated at the angle θ, that is:

y coordinate of green point = sin θ

As the angle θ changes, the red point moves up and down, tracing the red graph. This is the graph for the sine function. The faint vertical lines seen passing to the left are marking every quadrant along the circle, that is, at every angle of 90° or π/2 radians. Notice how the sine curve goes from 1, to zero, to -1, then back to zero, at exactly these lines. This is reflecting the fact sin(0) = 0, sin(π/2) =1, sin(π) = 0 and sin(3π/ 2) -1

A similar process is done with the x-coordinate of the green point. However, since the x-coordinate is tilted from the usual convention to plot graphs (where y = f(x), with y vertical and x horizontal), an “untilt” operation was performed in order to repeat the process again in the same orientation, instead of vertically. This was represented by a “bend”, seen on the top right.

Again, the green point is projected upwards (along the faint blue line) and this “bent” projection ends up in the top graph’s rightmost edge, at the blue point. The y-coordinate of this blue point (which, due to the “bend” in the projection, is the same as the x-coordinate of the green point) is the value of the cosine function evaluated at the angle θ, that is:

x coordinate of green point = cos θ

The blue curve traced by this point, as it moves up and down with changing θ, is the the graph of the cosine function. Notice again how it behaves at it crosses every quadrant, reflecting the fact cos(0) = 1, cos(π/2) = 0, cos(π) = -1 and cos(3π/2) = 0. — Figure 4: Sine and Cosine wave by Lucas Vieira, Public domain, via Wikimedia Commons

In figure 4, we can see an animation of the cosine and sine wave moving at the same frequency and how they are related to each other.

Summary

In the last three posts, we learned that sound is made up of tiny pressure waves which travel at 340 m/s. When these strike our ear drums, this in turn causes our basilar membrane to vibrate. Distinct vibrations on the membrane are heard as distinct frequencies.

We can graph the pressure waves of the sound. This is the same as the waveform graph in our DAW and is the same as the change in voltage of the signal going to our speakers. All signals going to our speakers have an amplitude, where taller is louder. Periodic sounds, like sine waves, also have a frequency, where a shorter wave length is a faster vibration and a higher pitch.

Waves can have the same frequency but be out of phase with each other, so their peaks and troughs do not line up.

Supplementary Reading

Everest, F.A. and Pohlmann, K.C. (2015). Master Handbook of Acoustics. Sixth edition. New York: McGraw-Hill Education. – Chapter 1

Activity

Materials

Audacity
Sonic Visualiser
A Microphone
An audio interface (or other way to get microphone input into your computer.)
A quiet corridor with a wall some meters distant
A tape measure
Optional: a room thermometer

Method

Place your microphone so it points at the wall. Start recording into Audacity. Stand behind the microphone. Clap. Stop recording.

Check your recording. You should have two impulses on the recording. One is the loud clap and the second is the echo of the clap. If these are too close together, move further from the wall.

Once you have a clean recording, export it as a WAV file and open it in Sonic Visualiser. Use the tape measure to measure how far you are from the wall.

Listen for when the first echo appears, and see if you can measure the distance in milliseconds using the display.

You might need to experiment a bit with the zoom controls, and possible other controls in Sonic Visualiser to make it clearer to see where the echo appears.

Also, it won’t necessarily be an exact point, so you may have to use your judgement.

Remember that the sound has to travel to the wall and back, so the total distance is double what you measured.

What was the speed of the sound. Is it what you expected? If you were able to measure the temperature, how much impact did that have on the speed?

Your Ear / Your Hearing

What’s happening in your ear? The outer ear, the pinna, helps you collect sound and holds your piercings, but the more interesting stuff, from a hearing perspective, is down the canal.

The middle ear, including the parts used for hearing. — Figure 1: The Middle Ear by Bruce Blaus CC BY 3.0 <https://creativecommons.org/licenses/by/3.0>, via Wikimedia Commons

Sound waves hit our tympanic membrane, which is to say, our ear drum. Three tiny bones, the smallest in our bodies, the malleus, the incus and the stapes, transmit the movements of the ear drum to an oval window. The oval window is attached to the inner ear, which is a rigid structure. The stapes pushes on the window, moving fluid inside the inner ear. Below the oval window is a round window. As the oval window is pushed in, the round window bulges out. This allows the fluid to move, as liquids are much less compressible than air.

This whole structure of the ear drum, the little bones and the window, take a movement in air and turn it into a movement in liquid.

The inner ear including the cochlea. — Figure 2: The Internal Ear by Bruce Blaus CC BY 3.0 <https://creativecommons.org/licenses/by/3.0>, via Wikimedia Commons

This liquid moves inside the cochlea, a snail shaped part of our ear. Inside that is the basilar membrane. This part of your ear is covered with tiny cells, called hair cells that wiggle in response to sound. The part of the membrane closest to the oval window responds to high frequency sounds, where the part furthest away responds to low frequency sounds.

When you hear a high frequency sound, the hair cells close to the oval window wiggle and send nerve signals to your brain. When you hear a low frequency sound, the hair cells further from the window are wiggling. These hair cells are fragile and can break in response to loud sounds. When they do break, they do not grow back. If you listen to ear buds too loudly, you can break these cells and your hearing will not come back. The hair cells closest to the ear drum are high frequencies and people tend to loose high frequency hearing first. When babies are born, their hearing is so sensitive that the lower threshold is just above individual air molecules hitting the tympanic membrane. People’s hearing gets worse from environmental factors including infections and exposure to loud sounds, but not from age. Wear protection to loud concerts and turn down your headphones to preserve your hearing.

When you are listening to two different frequencies, two different parts of your basilar membrane will wiggle. If those frequencies are far apart, you can hear each one individually. However, if the frequencies are close together, the parts of the basilar membrane that are wiggling can start to overlap. In this case, sometimes one sound can mask another, so we can’t hear both.

Image Sources:

Medical gallery of Blausen Medical 2014 (2014). WikiJournal of Medicine [Online] 1. Available at: https://en.wikiversity.org/wiki/WikiJournal_of_Medicine/Medical_gallery_of_Blausen_Medical_2014 [Accessed: 10 April 2024].