005 = Airplane Stacks and Backpack Hacks

**Airplane Stacks and Backpack Hacks** is the fifth episode of A Problem Squared.

### Show Notes

Problems featured in this episode:

* What went wrong with the audio of episode 003?
* The best place to put a backpack on a crowded train.
* How many Boeing 737s will fit?
* Making a perfect guest bedroom.
* Bonus: Bec has feedback on Matt's rice calculation

Support us on Patreon! (Link)

Review us on apple podcasts: (Link)

Twiiter: (Link)

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Listen to the BROKEN version of episode 003 and see how you hear Bec! (Link)

Wikipedia page on surround sound Matrix Decoding. (Link)

Watch Bec's flip-chart of "Non Je Ne Regrette Rien" by Edith Piaf. (Link)

This is the audio file of Non Je Ne Regrette Rien that Bec sometimes has problems with. (Link)

There are only 10,575 Boeing 737s which have been made and delivered. (Link)

Check out our instagram for photos of the 'Futuristic Garden' Bec gave Matt for their spare room. (Link)

### Summary

#### Audio Issues

In episode 3, Bec has an issue of sounding quite far away from the microphone, and the two of them wanted to talk about the issue.

Upon discovering the issue, they immediately pulled back the recording and their producer John fixed the issue. The problem was that despite recording everything as they normally did (except remotely) and doing the same edits as usual, Bec's waveform was out-of-phase, and it went unnoticed as it only affects some devices' playback functions.

So, they fixed the issue by isolating Bec's waveform, taking half of it and flipping it for the other half so it would be equalised. Matt gave a theory about the issue: mainly that Bec's recording was distorted between both the left and right channels, and when the opposite channels collided, they cancelled each other out, which made Bec sound faraway. So, by flipping one half around, they would be equal and the cancelling out would cease.

He also believes there may have been some screw up with matrix decoders in stereos within surround sound functions, but he doesn't have any expertise in it.

Bec also posed a problem to the listeners. Occasionally, she does flip-charts with jokes that follow along to songs. Recently, she had been having issues with an audio file of Edith Piaf's *Non Je Ne Regrette Rien* sometimes, usually at venues with smaller sound desks, where the instruments sound fine, but Piaf's voice comes out warped. So she would like to ask the listeners on what to do to fix that issue.

#### Backpack Hacks

Bridget B. on Twitter wrote into the podcast to ask them, "If you are on a crowded Tube train with a backpack, where is the best place to put it?" She mentioned that the floor if where people would stand, that if she carries it in her hand, it will lurch into other people's personal space. Bec tackled the problem, due to her being a big backpack fan.

She mentions that she had thought about this problem a lot, and that there were mainly 2 ways of solving it. The first was a dedicated 'backpacker carriage', in which half of the people were tall, and half were short, such that their backpacks would not bump into each other (possibly one on top of the other, suggested by Matt). However, she feels that this solution is not the best and would prefer the other.

Her other solution involves wearing your backpack on the front of your body, covering it with your top of choice, and putting a 'Baby on Board' sticker on you. This would probably result in people staying clear of you, as well as guaranteeing a free seat, though she notes that it may not be moral to some people.

#### Airplane Stacks

Receiving an email from someone named Rob, they were faced with this question: "As an air traffic controller, I am bound by certain restrictions for safety. 5 nautical miles laterally and 1000ft vertically... In a 3-dimensional space with a radius of 5 nautical miles and 1000ft high, how many planes could be crammed inside without touching?" He supposes that the aircraft would be frozen in time, and that they would be Boeing 737s pointing in the same direction.

Matt tackled the problem, crunching the numbers, and determining that the volume of a cylinder of 5 nautical miles (9260m) and a height of 1000ft (304.8m), as well as using the biggest version of the Boeing 737, the 737-900 (at 42.1m long, 35.8m wide and 12.5m tall).

Matt first went lazily and tried to count how many planes would fit in each layer and multiply by the number of layers, which leads to 24 layers of (with a gap of 27m between each) 177,998 planes per layer, leading to just over 4 *million* planes total (4,271,952 planes).

Matt then also took Bec's suggestion of interlacing the plane wings so they would be closer together and make save more space, making a rough calculation of 6.3 million planes (6,334,728 planes). This still assumes all the planes are still pointing in the same direction.

At the time, Boeing's website said that people had only order 15,115, of which 10,575 has been delivered (at the time). So, in theory, you could fit all of them in to the restricted airspace.

#### Perfect Guest Room

Matt posed a problem to Bec regarding his house. Having bought a new house with a spare guest bedroom, him and his wife hadn't done much with it, leaving it blank and mostly a place to keep other items (Bec can concur). With a comfy sofa bed, wardrobe, a few boxes in the corner, a bedside table with a lamp, and USB power outlets, what should he get to ensure he has the perfect guest room?

The first suggestion from Bec is to get rid of the boxes, obviously. She then starts asking Matt for details. He clarifies that he would like for people to feel welcome when they come over, mostly close friends and family. So far, they mainly range from young adult to 50s and stay for usually 1 night and sometimes 1 week (usually a work week).

She then suggests that he have some place to hang clothes up for those who stay for a week. Possibly creating some space in the wardrobe, which is currently half-full of suits and other clothes, would help. She then consulted her Twitter followers about what people like in their bedroom for research.

The favourite thing in the bedroom was a comfortable mattress or bed (which exists). Second was a toy, a figurine or a plush, which Matt could put some puzzles on the shelves. Third was a quilt or blanket, for comfiness. Fourth was their partner, which means Matt would put Lucy in the bedroom. Fifth was a pet, mostly cats, some other animals, and kids (added by Bec). The rest of the suggestions were very specific.

Bec got a futuristic garden kit to help solve Matt's problem. It's from the Science Museum, for ages 8+, so it works as a toy. With its life, it counts as a pet, and being space-related, it's related to Matt's partner (Lucy Green is an astronomer).

#### TL;DR

Q: What went wrong with the audio of episode 003?

* Bec's waveform was out-of-phase, so their producer fixed it by normalizing it.

Q: What is the best place to put a backpack on a crowded train?

* Ideal solution which requires the help of the railway companies: Backpacker carriage.
* Non-ideal solution for the solo person: Pretend to be pregnant?

Q: How many Boeing 737s will fit?

* In theory, at least 4.2 million-6.3 million.
* In practice, all of the Boeing 737s that have been made thus far.

Q: How can Matt make the perfect guest room?

* Get rid of the boxes, have a place to hang clothes, get a comfy bed, toy, a quilt, a partner, or a pet.

### AOB & Updates

003- The person who asked the question on optimal brushing was pleased with how thorough Bec went into answering, so it's a ding!

004-An example Matt used to explain how exponential growth worked involved using rice grains being collected in Bec's home, which he has assumed to be a 10x10x10m cube. After the episode, Bec measured the real dimensions of her flat to let him check his answer (8x6x2.1m). Calculating it, Matt's calculation was off by an order of magnitude (1000m³ vs 110m³), resulting in her house being filled in 18 rather than 20 days.