Wasn't Me

So I've been asked why I talk about Theranos and uBeam coverage. Well, it was first brought to my attention around Nov 12 last year when Meredith Perry retweeted a StartupLJackson tweet.

Theranos, blond woman running deep tech co. uBeam, blond woman running deep tech co. Hmm…https://t.co/OStYrWSHo5

— Startup L. Jackson (@StartupLJackson) November 8, 2015

So who first suggested the similarity in coverage? Not me.

Hypotwit

Following the CFO's departure from uBeam, I was reminded of a Tweet from a little while ago.

1/ There are just as many women on the planet as men. Just as pigment doesn't correlate w a person's intelligence, neither does a chromosome

— Meredith Perry (@meredithperry) December 4, 2015

Checking uBeam's LinkedIn info, it seems there are no women working at uBeam as either engineers or executives. I'm shocked to find that a CEO would say something that they themselves do not adhere to simply to get publicity. 

Edit: Someone pointed out, there might be women working there, they just might be hiding it on LinkedIn for some reason.

Acoustic Nonlinearity

I'm often asked "What is Acoustic Nonlinearity?" (No, really, it's actually surprisingly common. Bet you're jealous.)  Seeing as I have the smartest readers, both of them, I thought I'd do a basic explanation of it here. For something really detailed, I'd suggest these lecture notes, a book like "Nonlinear Acoustics" by Beyer, or "Diagnostic Ultrasound Imaging: Inside Out" by Szabo - I'll be borrowing some images from each of those in this post.

Nonlinearity means "not linear". Obviously. We tend to simplify things and think of them as linear - everything scales together. I kick a ball twice as hard, it travels twice as far - that's linear. I work 40 hours a week I get my salary, I work 80 hours a week and I still get the same salary - that's nonlinear. And stupid. The image below shows how this happens in real physical systems.

Every physical system is nonlinear, but we can often just simplify things and pretend they are linear, right up until they aren't. Once you have to include nonlinearities, things get really complex, really fast. Some smart people spend their lives working on this type of thing. With sound this can happen in a number of ways, some beneficial, and some not.

With acoustic nonlinearity, what happens is this: An acoustic wave travels through a medium - this can be through human tissue for a medical scan, or through air for a sound. You can keep increasing the amplitude of this wave, and as you double the amplitude the wave gets twice the size. At some point, there's enough energy in this wave that at the top half of the cycle it actually compresses (squeezes together) the medium, and at the bottom half it's a rarefaction (pulls it apart). The propagating medium gets denser at the top half, and less dense at the bottom. 

Once this starts to become significant, the density change actually starts to effect the velocity of the acoustic wave - the denser part goes faster, the less dense part slower - and so the wave starts to 'tilt' and one half catches up with the other. That's what you can see happening in the top parts of the image below.

Once the top part of the wave catches up with the bottom part, the middle row of the image, then you get a 'saw tooth' wave. What is happening is that energy that is at the fundamental driving frequency starts moving higher in frequency - for example in a medical ultrasound image if you send out at 1 MHz and nonlinearity happens, you create signal that's 2MHz, 3 MHz etc by 'sucking away' some of the energy at 1 MHz.

If you've had a medical ultrasound scan in the last 15 years you've probably benefited from this. You can use acoustic nonlinearity to get a much better resolution in your scan with that 2 MHz component without some of the difficulties of building a system to transmit at that higher frequency.

The downside to pushing all this energy higher in frequency is that if you need to use it at the lower frequency, well it's gone from there, and more critically the attenuation is almost always higher at higher frequencies. Attenuation is where you lose some of the energy of the acoustic wave over distance, so basically higher frequency waves die off faster. The bottom line of the image above shows the saw tooth wave getting smoothed out by attenuation.

Szabo, Chapter 12, has some more great images.This shows how the wave changes as it travels out, and the graphs on the left show the shift of energy away from the fundamental frequency to the higher harmonics.

How far can a wave go before this occurs? Well, there are some basic equations that can tell you when it does. If you don't like maths, I've put all of that at the bottom and I'll cut to the interesting example right away. For those of you who really like maths, see below, then check out the lecture notes linked to above, or go to Chapter 3 of Beyer's book.

TL;DR. Nonlinear distance gets shorter with:

• Increasing frequency
• Increasing wave amplitude
• Increasing nonlinear properties of the medium

Let's pick a couple of examples and test them. I'm going to take some acoustic numbers from here. Two cases, 45 kHz and 145 dB, and 75 kHz and 155 dB. (dB is a logarithmic way of referring to sound pressure, in this case that's about 500 Pa and 1600 Pa respectively).

For 45,000 Hz and 500 Pa in air, that's about 30 cm when nonlinearity starts.

For 75,000 Hz and 1600 Pa in air, that's about 5 cm when nonlinearity starts.

Wow that's a short distance (it's actually slightly longer than that in reality due to attenuation, but not much). And it doesn't tend to happen slowly - it ramps really quickly and within around 1.6 times that distance (48 and 8cm respectively), huge amounts of the energy are moved to higher frequencies. 

Then the increased attenuation in air removes that acoustic energy entirely, converting it to heat. To give you an idea of the degree of nonlinearity, if you look at the energy available at 1 meter at the fundamental frequency with 155 dB vs 145 dB, then you've driven 10 times harder, but you only get about half as much again (around 95% of the additional energy is lost as heat). Not very efficient. 

This is what's known as saturation - when you keep driving harder and harder, but you just can't get any more energy in. The medium (in this case air) is saturated and can't really absorb any more, most of what you add is lost. There are some basic equations to work this saturation pressure out, one is listed on page 510 of Szabo, it's detailed below. For air, at 45 kHz, at 1 meter, it's about 450 Pa, or 144 dB. Past that value of pressure, at that frequency, you're just running faster and faster to stand still, and getting very hot in the process.

So there you have it, a basic explanation of nonlinear acoustics. Here's a summary:

• Nonlinear acoustics are simple in concept, really complicated to fully understand
• Once you start driving an acoustic wave hard, eventually it becomes nonlinear
• Nonlinear acoustic waves start shifting energy from the fundamental to higher frequencies
• Attenuation converts that energy to heat, sometimes very quickly
• Onset of nonlinearity is sudden, and can happen very close to the source
• Propagating media such as air can saturate when you drive hard, which means it can't take any more energy

Stop reading here if you don't like maths.

Some equations (Beyer page 104):

Nonlinear Distance = 1. / ( Beta * Mach Number * Wavenumber )

Beta (for air) = 1.2
Mach Number = Pressure / ( Acoustic Impedance of Air * Sound Velocity in Air)
Wavenumber = 2 * PI * Frequency / Sound Velocity in Air

The Acoustic Impedance of Air is 410 Rayls, and the Sound Velocity in Air is 343 m/s.

So :
Mach Number = Pressure / 140600
Wavenumber =  Frequency / 56

And

Nonlinear Distance = 1. / (1.2 * ( Pressure/140600) * ( Frequency / 56 ))
Nonlinear Distance = 6500000 / ( Pressure * Frequency )

Finally (Szabo, Page 510)

Saturation Pressure = ( Acoustic Impedance of Air * Sound Velocity in Air ^ 2 ) / ( 2 * Beta * Frequency * Distance )
Saturation Pressure = 20100000 / ( Frequency * Distance )

Abandon Ship

Today I looked at the LinkedIn profiles of the uBeam staff and was interested to see that Monica Hushen, the CFO, has left the company. Hushen was lauded in the tech press (I won't call it journalism) as a heavyweight and an amazing win for uBeam.

"Perry has hired some hardware industry veterans to whip the business into shape. Former Apple and Palm finance leader Monica Hushen will be uBeam‘s new CFO"

Now I need to first comment, that the engineering team was sorely pissed at the idea that we needed whipped into shape by two people who we felt had no idea what to do at a technical startup in the R&D phase. We were almost as pissed as when another article was placed in Techcrunch talking about uBeam achieving the physically impossible, such as charging through a pocket. In my opinion, the addition of these two "C's" marked the end of any hope of the company achieving anything - I left two weeks after that article was published, and I think history is proving my feeling correct.

But back to Catbert, as she was sometimes referred to. Bizarre that a person so critical to the company, so important, and so knowledgeable as to the state of the company and its dealings would leave, and maybe even leave prior to the 1 year vesting cliff. It's almost as if she has no faith that the company will ever achieve anything of value and it's best to leave now rather than waste time on a sinking ship.

This CFO is leaving at the exact time that, according to numbers published by Mark Suster the lead uBeam investor, that the company needs to start raising their next funding round - around 6 months prior to an estimate of their funds running out.

When I left it was an ugly departure, but was reported to the investors as "the VP Engineering left for personal reasons" - personal reasons being "sick of putting up with this bullshit". I wonder what uBeam's excuse for Hushen will be? "Spending more time with her family", "Having achieved everything she had set out to, it was time to move on to other things", or like me has she left for "personal reasons"? I'm betting on the first.

Note: Since this afternoon, Hushen has relisted herself as working at uBeam on LinkedIn, no doubt someone spotted it and she's trying to dodge the press. But she's left.

Note2: Now LinkedIn has the new position as "CFO at Wonder Workshop".

Toddler vs CEO

Someone sent this to me and asked if it was what it was like having Meredith Perry as a CEO. I told them no, it wasn't.

I don't recall Meredith ever having special made-up words.

Beat me to it

So I was going to do another amazing post about how poor journalistic standards are in part contributing to money being wasted in startups, but Vanity Fair and the Twitterverse beat me to it.

The secret culprit in the Theranos mess is the tech press, which may be as responsible as Elizabeth Holmes. https://t.co/RhcSov69nX

— Nick Bilton (@nickbilton) May 2, 2016

@nickbilton @paulvieira A similar story is Ubeam. Electricity transmission via ultrasound that's never been demonstrated to be efficient.

— Stephen Green (@StephenGreen82) May 3, 2016

True Genius

Maybe Elizabeth Parish should start this company with them?

We're pleased to reveal our partnership with ubeam. Soon you'll have your finger pricked ultrasonically while you're sitting in Starbucks.

— Not Elizabeth Holmes (@NotLizHolmes) February 27, 2016