An­drea PureAu­dio Mi­cro­phone Devel­op­ment Kit

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The two pages you’re read­ing now were writ­ten on the morn­ing of this col­umn’s dead­line. Not be­cause I’m a ter­ri­ble pro­cras­ti­na­tor – this time around, any­way – but be­cause the orig­i­nal re­view I wrote prompted the com­pany be­hind the prod­uct to com­pletely re­think its ap­proach to mar­ket.

Orig­i­nally, you’d have been read­ing a scathing re­view of the Pure Au­dio Speech Devel­op­ment Kit (SDK) from An­drea Elec­tron­ics, a long-stand­ing name in the au­dio in­dus­try. Billed as the one-stop sys­tem for high-qual­ity speech con­trol of In­ter­net of Things (IoT) and voice-as­sis­tant projects run­ning on a Rasp­berry Pi, the SDK proved to be any­thing but.

Dur­ing test­ing, the kit was found to have sev­eral is­sues. For starters, there was a manda­tory USB sound card that was tied to the soft­ware purely for li­cens­ing pur­poses, hav­ing no ded­i­cated hard­ware or spe­cial­ist com­po­nents over a £5 unit from any other man­u­fac­turer. There was also an out­dated make­file that sim­ply wouldn’t work with­out man­ual mod­i­fi­ca­tion, and an au­dio fil­ter li­brary that can’t run echo can­cel­la­tion on any Pi de­vice below a Rasp­berry Pi 3.

In ad­di­tion, the li­cence pre­cluded the user from mod­i­fy­ing the source code of the sam­ple ap­pli­ca­tion, ren­der­ing it use­less. Then there was the sam­ple ap­pli­ca­tion it­self, which was less a start­ing point for devel­op­ment and more a bare bones demo bet­ter suited to show­ing off An­drea’s au­dio tech­nol­ogy at trade shows.

Far from al­low­ing the user to de­velop im­pres­sive Siri or Alexa style ap­pli­ca­tions, the SDK in­stead had only two func­tions: lis­ten for a pre-set trig­ger phrase, ‘Hello Blue Ge­nie’, and trig­ger a ten-sec­ond record­ing. Ad­di­tional fea­tures in the form of spe­cific com­mands can be added, but they’re avail­able only in ex­tremely lim­ited ‘vo­cab­u­lary packs’ as paid add-ons. Th­ese packs re­quire you to state the com­mand ex­actly as writ­ten, mak­ing ‘turn on the light’ a valid com­mand but ‘turn the light on’ an in­valid one, and come with no ac­tual abil­i­ties, bar print­ing a mes­sage to the ter­mi­nal con­firm­ing that a com­mand has been de­tected.

To its credit, An­drea Elec­tron­ics took the news that it had per­haps not de­vel­oped the SDK to the point it had promised with aplomb – and, the day be­fore this col­umn was due, per­formed a dra­matic volte-face. No longer was it the PureAu­dio Speech Devel­op­ment Kit, but the Noise-Can­celling Mi­cro­phone Devel­op­ment Kit.

No longer was it po­si­tioned as a means for hob­by­ists to play with voice con­trol, but in­stead a jump­ing-off point for ex­pe­ri­enced de­vel­op­ers ea­ger to ex­per­i­ment with An­drea’s tech­nol­ogy. The vo­cab­u­lary files, mean­while, are still set for launch, but they’re no longer a pri­mary fo­cus of the prod­uct.

The real meat of the prod­uct, Doug An­drea ex­plained in an email ex­change, is the fil­ter li­brary. Us­ing the au­dio in­put from the bun­dled stereo mi­cro­phone – a de­sign that will be im­me­di­ately fa­mil­iar to any­one who pur­chased se­lect Asus moth­er­boards a decade ago as an in-pack free­bie – the fil­ter li­brary al­lows for rel­a­tively fine-grained con­trol of the in­com­ing stream.

The con­trols in­clude far-field en­hance­ment, a fancy new name for ‘mi­cro­phone boost’, which am­pli­fies quiet

sig­nals. There’s also the flag­ship noise re­duc­tion fea­ture, along with echo can­cel­la­tion, which pops and crack­les on any Pi de­vice below a Pi 3.

Fi­nally, the beam­form­ing con­trol at­tempts to ‘zoom in’ on sub­jects not di­rectly cen­tred in front of the mi­cro­phone.

Test­ing th­ese fea­tures, there’s no deny­ing they work. Sim­u­lat­ing a noisy fac­tory set­ting – the sort of in­dus­trial en­vi­ron­ments into which An­drea has been sell­ing its mi­cro­phone tech­nol­ogy for years – and tog­gling the noise re­duc­tion did, in­deed, con­sid­er­ably re­duce the back­ground noise at the cost, typ­i­cal of such fil­ters, of mak­ing the recorded speech sound a lit­tle muddy and ar­ti­fi­cial.

Un­for­tu­nately, there’s a ma­jor caveat. Un­like the days when the Su­perBeam was bun­dled with Asus moth­er­boards, along with a Win­dows driver bun­dle for con­trol of all th­ese shiny fil­ter modes, the Rasp­berry Pi ver­sion comes with only the ba­sic sam­ple ap­pli­ca­tion, so the only way to use the fil­ters is to write your own ap­pli­ca­tion. If you’re hop­ing to im­prove the qual­ity of your Google Hang­out ses­sions or Au­dac­ity record­ings, you’re go­ing to be dis­ap­pointed.

Even if you’re will­ing to write your own ap­pli­ca­tion, the fil­ter li­brary is en­tirely soft­ware-based, which is why the kit is only func­tional on the pow­er­ful Rasp­berry Pi 3, and eats be­tween 30 and 40 per cent of a CPU core’s re­sources while run­ning the hot­phrase de­tec­tion. Had the manda­tory USB sound card – based on a C-Me­dia CM6400 chip, de­signed for in­clu­sion in low-cost USB head­sets – in­cluded ded­i­cated pro­cess­ing hard­ware to jus­tify its manda­tory use, the kit could have been com­pat­i­ble with the whole Rasp­berry Pi range.

The An­drea PureAu­dio Mi­cro­phone Devel­op­ment Kit is avail­able to buy from­drea­elec­tron­ for $49.95 US (around £43 inc VAT), with vo­cab­u­lary files – which you can’t make your­self, nor edit in any way to add to the very lim­ited op­tions on of­fer – priced at $9.95 US (around £8.54 inc VAT) each.

Orig­i­nally the Speech Devel­op­ment Kit, An­drea’s Pi bun­dle has taken an abrupt shift in tone

The ‘Su­perBeam’ mi­cro­phone will look fa­mil­iar to buy­ers of some Asus moth­er­boards a decade or so ago

The USB sound card is a cheap C-Me­dia CM6400 af­fair, but the soft­ware won’t work with­out it

The noise re­duc­tion fil­ter def­i­nitely works, but you can’t use it with third­party ap­pli­ca­tions

The ‘far field en­hance­ment’ mode does a good job of boost­ing weak sig­nals, but can’t be au­to­mat­i­cally ac­ti­vated

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