0:03

and so what we’re doing Barry is we’re

0:06

exploring a series it’s – this is kind

0:09

of a the first of a series of month two

0:14

months long exhibition online we’re

0:17

taking Michael Sorkin I don’t know if

0:20

you knew the late architecture critic

0:22

who passed recently he had avid critic

0:27

and wonderful inspiration in terms of

0:31

the public realm and what is the essence

0:37

of architecture not not necessarily just

0:39

the built form but what are the equity

0:40

aspects of architecture right and so

0:44

there’s an essay that he did called 250

0:46

things that in architecture know and so

0:49

I’m kind of picking apart some of those

0:52

things and then exploring them more

0:53

deeply so the essay is in the book what

0:57

goes up the right and wrongs to the city

0:59

and so we’re gonna be discussing how

1:02

sound travels and what his his phrases

1:06

were basically what is the distance that

1:09

a shout carries and what is the distance

1:11

of a whisper and so those are the two

1:14

things that we’ll be exploring and

1:16

that’s why I thought sound you know how

1:17

sound travels makes makes good sense for

1:20

us to discuss sure so I guess I would

1:24

start with just for I think for decades

1:28

you’ve consulted on sound in the built

1:30

environment so I wondered if maybe a

1:33

good place to start is the field

1:34

recording because to understand how

1:36

sound travels you have to start by

1:39

observing sound movements correct it

1:44

certainly helps you know to actually

1:49

have an understanding of the way things

1:51

are experienced recording isn’t

1:55

necessarily the first step in that the

1:58

critical listening is and that’s just

2:02

spending the time to listen to the way

2:05

sound behaves in the environment back in

2:08

my my early CBC radio technician days

2:11

that’s one of the things they taught you

2:13

about recording was just listen to the

2:16

way it sounds

2:17

like say a musical group sounds into

2:20

space walk around and then decide then

2:24

where you put microphones to capture

2:26

that recording and that’s that’s

2:30

certainly a big part of establishing

2:34

what a reasonable acoustical environment

2:38

sounds like mm-hmm would you say so

2:44

maybe I’ll just ask what’s the most

2:46

interesting field recording you’ve

2:48

captured well certainly that the most

2:52

unusual one was that recording in the

2:54

cooling tower at Alma Washington the

2:57

south saw decommissioned nuclear plant

3:01

that was just trippy because literally a

3:07

whisper like at the quietest you would

3:10

talk to somebody say three or four feet

3:12

away it came back to you because it’s a

3:15

perfectly circular focusing field in

3:19

there so even the quietest sounds would

3:23

be reflected back with a sizable delay

3:27

on the echo mm-hmm very very trippy and

3:31

so the sound is bouncing or what we

3:35

might call a beret ssin is that right

3:38

yeah and there’s two aspects to that

3:41

there’s a direct sound of first

3:44

reflection or multiple reflections and

3:46

that would be what most people call an

3:48

echo and then reverberation is the sound

3:52

bouncing around in decaying in level

3:55

each time it essentially passes by you

3:59

so how do we define a reverb or

4:02

aberration time reverberation time is

4:06

the time it takes for a sound usually

4:09

the most easy way to think of it as like

4:12

an impulse like a clap or something to

4:15

decay to one millionth of the original

4:18

level and that’s 60 decibels so by the

4:22

time it drops to minus 60 that’s that

4:26

decay slope is considered the

4:27

reverberation time

4:30

and so when you were in that cooling

4:32

tower what was happening to that sound

4:35

how was it decaying

4:37

well the interesting thing about the

4:39

cooling tower is that there wasn’t

4:42

really a reverberant field because it

4:44

wasn’t truly enclosed there’s the little

4:48

legs that you you see in the pictures of

4:51

those things and you think well you know

4:53

how tall can those be but they’re like

4:55

15 meters tall so essentially it’s

4:58

completely open around the bottom and

5:00

open at the top so you don’t hear

5:03

reverberation but you hear repeated

5:05

flutter echoes that because they’re it’s

5:09

perfectly circular they come back at you

5:12

from all directions pass through each

5:15

other and then hit the walls and then

5:17

are focused again and because the

5:20

cooling tower is curbed vertically they

5:24

also travel up and then sometimes

5:28

they’ll travel back down again so it is

5:32

just a strain to sort of surround sound

5:36

effect for echoes because they literally

5:39

swarm around you as that and then they

5:41

kind of go up and out the top and if you

5:46

eye binaural recording so you actually

5:49

have a recording system that simulates

5:51

the human ears you hear all that spatial

5:54

differentiation so you hear where they

5:57

come from where they go – it’s very cool

6:00

and what’s interesting from the layman’s

6:04

perspective from someone that doesn’t

6:05

know much about sound is that when you

6:08

think about measuring sound like the

6:10

question you know what’s the distance it

6:12

travels or what’s the distance of a

6:14

whisper it’s not as simple as just

6:17

taking a measurement of how fast sound

6:19

travels but it’s really about what do we

6:22

hear and how audible is it and so the

6:25

reverberation on the echo are kind of

6:27

affecting our ability to hear is that

6:30

correct yeah it they certainly affect

6:32

the ability to understand what’s being

6:35

transmitted

6:37

you know speech is made up of phonemes

6:40

you know syllables and parts of

6:42

syllables

6:43

and if the reflections and reverberation

6:46

walk on top of those you can lose the

6:49

ability to understand things so as the

6:51

reverb time increases and so you’re in

6:54

you know anything from a stairwell to a

6:56

hockey arena the the speech

7:00

intelligibility is greatly reduced

7:01

because now as each new syllable comes

7:04

along that’s being stomped on by all the

7:07

other reflections of reverberation and

7:10

that’s why first designing for speech

7:13

intelligibility like in a classroom or a

7:16

theater you have to be very conscious

7:19

conscious about the the arrival time the

7:25

a level of reverberation the level of

7:27

reflections when they come where they

7:30

come from so it’s it’s quite a balancing

7:34

act in that process and so I think you’d

7:38

mentioned when we talked earlier before

7:41

this interview about the idea of you

7:44

know we talked about the Elma cooling

7:46

tower the decommission tower there was

7:48

also a room full of clothes that would

7:51

be that kind of idea of where sound

7:53

doesn’t reverberate that’s the opposite

7:56

of the cooling tower in a sense what’s

7:59

condition for a whisper well for a

8:03

whisper that the controlling element is

8:06

likely going to be background noise

8:09

because the whispers starts off quieter

8:12

you know a whisper might a stage whisper

8:14

might be say maybe 45 dB at the other

8:20

actors location and because sound drops

8:26

in level at 6 DB per doubling a distance

8:30

at some point that sound drops down to

8:33

the level where it matches her as is

8:36

masked by the background noise in the

8:38

room so again for a theater the goal is

8:41

to get the the noise level down low

8:44

enough that people can hear something

8:47

like a stage whisper at a great distance

8:50

outdoors a whisper gets pretty quickly

8:52

not by you know traffic noise wind noise

8:55

through the leaves and that’s

8:58

but sound behaves at a shout and a

9:01

whisper the same way when it leaves the

9:04

somebody’s mouth it behaves in the same

9:06

fashion when one is sending that said no

9:12

whether it’s a whisper or a shout it

9:15

depends on area where the sound how far

9:19

the sound is going you talked a bit

9:22

about the field I wonder if you could

9:23

bring that in like the idea of when when

9:26

one means to direct the sound of the

9:28

shout it can go farther than if it’s

9:30

spread out why is why is that normally

9:34

most sound sources have an

9:39

omnidirectional output or very close to

9:42

it

9:42

so if you’re talking the level of your

9:46

voice behind you is very similar to what

9:49

it is out in front of you so the sound

9:52

spirit spreads as a hemisphere that’s

9:56

spreading across the ground each time

9:59

you double the radius you increase this

10:02

surface area that’s fear by four times

10:05

so it has a very predictable drop in

10:09

level so it would be 60 beep every time

10:13

you double the distance so the first say

10:17

if somebody’s a meter away and you talk

10:20

to them at a reasonable level if they

10:23

move 2 meters away it’s 60 be quieter if

10:26

they move 4 meters away

10:28

it’s another 60 be quieter now once you

10:33

start to get to really long distances

10:35

there’s some other factors that come

10:37

into play but that’s you know there’s

10:40

the atmosphere absorb sound it depends

10:43

on humidity and temperature but

10:45

generally you can think of it in those

10:47

terms so that if you want to get

10:49

somebody’s attention who say you know

10:52

half a baseball diamond way you would

10:54

cup your hands around your mouth to

10:56

direct the sound more towards them so it

11:00

isn’t the hemisphere anymore it’s now

11:02

say a quarter of a sphere you’ve sort of

11:05

taken a conical section and redirected

11:09

that sound towards them

11:10

so you’ve effectively shrunk the area

11:12

rec yeah so just last question back to

11:17

the whisper if we were to find a perfect

11:21

and I think we talked a little bit about

11:22

a corner and what happens in the corner

11:25

so it’s the corner a good place where

11:27

whisper or what happens in that corner

11:29

situation every time you reduce the area

11:33

that you’re either Purdue or projecting

11:37

sound into or hearing sound back from

11:41

you increase the effective level the

11:44

same way is when you cup your hands

11:46

around your mouth you tighten up the

11:49

direction that sound is traveling if you

11:53

add one wall you increase the level by 3

11:56

dB if you add a second wall with a

11:58

right-angle corner that’s 6 dB if you

12:02

add the two walls and the floor that’s 9

12:05

DB so that’s subjectively just about

12:09

twice as loud so if you were gonna try

12:12

to project a whisper the best place to

12:15

do it is back right up against a corner

12:17

in a room and it would actually travel

12:21

all the sound instead of traveling

12:22

behind you would all travel forward out

12:25

of that corner or if you had a secret

12:28

that you really didn’t want everyone to

12:30

hear you might choose not to be in a

12:32

corner yes

12:34

or you know there’s the other famous

12:36

aspect of acoustics is whispering

12:39

galleries you know some of the the big

12:43

cathedrals with the the curved ceilings

12:47

and round construction that has that

12:50

same effect as the Alma cooling tower

12:53

where a whisper on one side can be

12:56

picked up by somebody just like you came

12:59

up and talked to them in their ear

13:01

across the dome which is the reason that

13:06

you generally try to avoid dome shape

13:09

facilities in almost every practical

13:12

application because it creates all kinds

13:16

of interesting acoustic challenges right

13:18

so the dome in a performance activity

13:22

becomes much

13:22

challenging because it’s collecting

13:24

everything everything and interestingly

13:27

enough as you if you were at the center

13:29

everything would come back to you as

13:31

though it you were wearing headphones

13:34

and then as you move off Center you end

13:38

up with a space exactly opposite you

13:41

where all of that sound is focused and

13:44

as you move further away from there

13:46

until you get to the outside edge you

13:49

know that focal point moves and then it

13:51

goes around to the point again on the

13:53

outside wall where it would literally

13:55

sound like somebody else has headphones

13:57

on so yeah it creates some interesting

14:01

challenges and spaces where that isn’t

14:04

appropriate yeah well I want to thank

14:07

you there’s a lot more we could go into

14:09

depth on but I really wanted just a

14:11

short little introduction for everyone

14:14

to hear of our conversation and I’m

14:16

going to thank you very much fear for

14:18

your time and for helping us to really

14:20

think about sound not necessarily just

14:23

as the distance it’s not just about the

14:26

a distance there’s a lot more complexity

14:27

involved and reverb and echo and shape

14:31

of surfaces and the number of surfaces

14:34

all of those things have a difference

14:35

yeah absolutely

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