The Archaeology of Sound; The Oracle Chamber Of Malta’s Hypogeum Of Ħal-Saflieni

Danbones
reply to post by Harte

 

it doesan't?
prove it

only this time use links that don't impeach your self

ACOUSTIC PROPERTIES OF LIMESTONES FROM THE NORTH-CENTRAL PACIFIC,
DEEP SEA DRILLING PROJECT LEG 621

www.deepseadrilling.org...
AGAIN from your link

edit on 3-3-2014 by Danbones because: (no reason given)

and again again:

The density-velocity relationship of the carbonates shows excellent correlation with Gardners curve for limestone. The
general Gardners curve, however, underestimates the velocities of the volcaniclastics. Laboratory porosity-velocity trends of the
carbonates are consistently 5% to 20% higher than those predicted by the time-average equation using the correct matrix velocities.
Similar crossplots for the volcaniclastics show a division into two distinct subgroups, each corresponding to a time-average
equation with a different matrix velocity, which suggests that progressive diagenetic alteration of the volcaniclastics has decreased
the matrix velocity. The VjJVs
ratios of the carbonates do not discriminate mineralogic composition. Laboratory measurements,
under effective pressure simulating in situ conditions, are 5% to 25% higher than analyses of velocity made aboard JOIDES
Resolution under atmospheric pressure.
The carbonates at Site 866 have a considerably wider range of acoustic impedance than the basalt. As a consequence, the
contact between the carbonate succession and the underlying basalt basement in many drowned Cretaceous guyots of the equatorial
Pacific Ocean may be difficult to image seismic-reflection profiles

Again, you're quoting a source discussing the propagation of sound waves through stone beds. We were discussing the reflection of sound waves off the face of a stone surface.
Every different type of stone will ehibit "unique" properties when examining how sound travels through the stone. This is even true of different beds of the same type of stone, as your quote indicates.

However, as another poster pointed out already, the reflection of sound off a stone surface depends almost completely on the smoothness of that surface, and not on what kind of stone is behind the surface.

The chambers this thread is concerned with are dug unto limestone because that is the stone that is there, not because limestone has some "unique" quality regarding sound reflection. That is, any stone will reflect sound in exactly the same way, given a similar surface treatment.

Obviously, this includes granite. But my point was, granite may be prettier than limestone, but the Greeks used limestone for amphitheaters because it is MUCH easier to quarry, shape and smooth than other local stones available in the necessary quantities.

If Malta had granite bedrock, a chamber dug unto it would provide exactly the same sound reflecting properties as the current limestone one. But it's quite likely that, if the bedrock had been granite, they wouldn't have excavated such chambers at all due to the difficulties inherent in digging through granite.

Danbonesdoesn't matter the fundamental frequency...there will be harmonics in pretty much all human defined ranges which are arbitrary and reflect the definitions imposed by scientific disciplines

Harmonics exist for every fundamental frequency of anything that can be though of as vibrating, including any frequency of electromagnetic waves. There is nothing arbitrary about this fact. But ranges of hearing can, in a sense, be thought of as abitrary, since some people hear a wider range of audible frequencies than others.

Harte

Sound Absorption Coefficients

www.acousticalsurfaces.com...

geeez
phascepalm

Concrete Block – Light, Porous .36 .44 .31 .29 .39 .25
Concrete Block – Dense, Painted .10 .05 .06 .07 .09 .08
Gypsum Board – 1/2″, Nailed to 2×4, 16″ O.C. .29 .10 .05 .04 .07 .09
Marble or Glazed Tile .01 .01 .01 .01 .02 .02
Plaster – Gypsum, or Lime, Smooth Finish on Tile or Brick .013 .015 .02 .03 .04 .05
Plaster – Gypsum, or Lime, Rough Finish on Lath .14 .10 .06 .05 .04 .03
Plaster – Gypsum, or Lime, Smooth Finish on Lath .14 .10 .06 .04 .04 .

go the link look up what the numbers mean


eta..repitition for emphasis
ABSORPTION COEFFICIENT CHART
www.sae.edu...

everything has an absorbtion /reflection coefficient:
limestone, granite, peanut butter,....even you Harte




web.natur.cuni.cz...

However, as another poster pointed out already, the reflection of sound off a stone surface depends almost completely on the smoothness of that surface, and not on what kind of stone is behind the surface.

care to back that up with something a little more substantial then "another poster"?
cause right now you are just talking out your butt

The terms source, receiver and reflecting interface are introduced. Sound energy travels through different media (rocks) at different velocities and is reflected at interfaces where the media velocity and/or density changes. The amplitude and polarity of the reflection is proportional to the acoustic impedance (product of velocity and density) change across an interface. The arrival of energy at the receiver is termed a seismic event. A seismic trace records the events and is conventionally plotted below the receiver with the time (or depth axis) pointing down the page. Click here to see a movie illustrating wave propagation. The colour background is the velocity field.

www.xsgeo.com...


densities of various rocks as per the above little giblet of haha you are wrong Harte
geology.about.com...

Danbones

Sound Absorption Coefficients

www.acousticalsurfaces.com...

geeez
phascepalm

Concrete Block – Light, Porous .36 .44 .31 .29 .39 .25
Concrete Block – Dense, Painted .10 .05 .06 .07 .09 .08
Gypsum Board – 1/2″, Nailed to 2×4, 16″ O.C. .29 .10 .05 .04 .07 .09
Marble or Glazed Tile .01 .01 .01 .01 .02 .02
Plaster – Gypsum, or Lime, Smooth Finish on Tile or Brick .013 .015 .02 .03 .04 .05
Plaster – Gypsum, or Lime, Rough Finish on Lath .14 .10 .06 .05 .04 .03
Plaster – Gypsum, or Lime, Smooth Finish on Lath .14 .10 .06 .04 .04 .

go the link look up what the numbers mean

eta..repitition for emphasis
ABSORPTION COEFFICIENT CHART
www.sae.edu...

everything has an absorbtion /reflection coefficient:
limestone, granite, peanut butter,....even you Harte

I'm aware. Too bad you can't read your own link, even after you quoted it!

Please don't assume that I don't know about these coefficients. As a mechanical engineer, I was made aware of engineering materials and their properties while in college. Not that I used them in my work, however, nor did I use, for example, thermal expansion coefficients, which I also know much about.
As a current teacher of physics, and having just recently finished teaching my unit on waves and sound, I assure you that you're not telling me anything I don't know. In fact, you don't strike me as having the background here to even hold your own. My having to prod you continuously to notice that you had been looking up transmission of sound waves through stone, which is not the topic we are discussing, is more than enough evidence of this.

Here's (I think) the statement I made that you seem to be responding to:

Harte
It's quite simple to grasp that stone blocks the transmission of sound, which is what you quoted.
So does granite, sandstone, marble, gneiss, brick and concrete, for that matter.
Harte

From your second link:

Floor materials------------------------125 Hz---250 Hz---500 Hz---1 kHz----2 kHz---4 kHz
Concrete (unpainted, rough finish)---0.01----0.02-----0.04-------0.06------0.08----0.1
Concrete (sealed or painted)---------- 0.01----0.01-----0.02-------0.02------0.02----0.02

FYI:
Limestone acoustic absorption coefficients:

Kashigeo PPX Limestone.
Bulk spec. gravity --- 2,48 gr/cm3
Absorption coefficient --- 3,07%

Vicente Beige Limestone.
Bulk specific gravity --- 2,56 gr/cm3
Absorption coefficient --- 1,73

Vicente Blue Limestone.
Bulk spec. gravity --- 2,62 gr/cm3
Absorption coefficient --- 1,80 %

Branco do Mar.
Bulk specific gravity --- 2,36 gr/cm3
Absorption coefficient --- 4,8 %

More listed here.
Those limestone coefficients are averages over the range given in your two links. To compare, you'll need to calculate an average over the range provided at your linked site.
So, now it's my turn to be condescending: To calculate an average, add up all the coefficients across a single horizontal line, then divide that sum by the number of coefficients you used (in this case, that would be 6.) To begin comparing, in the limestone values I provided move the decimal (that's the comma in these quotes) two places to the left and compare those numbers with yours for brick and for concrete. Also, please note that I said concrete not concrete "foam" blocks.

Danbones

HarteHowever, as another poster pointed out already, the reflection of sound off a stone surface depends almost completely on the smoothness of that surface, and not on what kind of stone is behind the surface.

care to back that up with something a little more substantial then "another poster"?
cause right now you are just talking out your butt

Perhaps you are using your own butt to read the info at the links you yourself provided.
I repeat:

Floor materials------------------------125 Hz---250 Hz---500 Hz---1 kHz----2 kHz---4 kHz
Concrete (unpainted, rough finish)---0.01----0.02-----0.04-------0.06------0.08----0.1
Concrete (sealed or painted)---------- 0.01----0.01-----0.02-------0.02------0.02----0.02

Same material, different finish. Gee, that sounds familiar.

Danbonesdensities of various rocks as per the above little giblet of haha you are wrong Harte
geology.about.com...

The above is an indication that you are unaware that the density and acoustical properties of stone always vary somewhat, even within the same stone bed.
But, once again, I see you're using sound transmission data instead of sound absorbtion data. This is interesting in it's own right and is often used in geology (even in the first Jurassic Park movie.) But, unless you're trying to comment on sound reflection at the contacting surfaces of limestone joints in a Greek amphitheater, it really has no bearing on our topic.

Harte
EDIT: Oh, I'm sorry, I see you didn't mention brick, even though this is from your link:

Materials
Brick – Unglazed
125Hz 250Hz 500Hz 1000Hz 2000Hz 4000Hz
.03 .03 .03 .04 .05 .07

Brick – Unglazed, Painted
125Hz 250Hz 500Hz 1000Hz 2000Hz 4000Hz
.01 .01 .02 .02 .02 .03

Huh, would you look at that. Plain unpainted brick performs as well as some of the limestones. Yet painted brick outperforms even the limestone. Again, that seems quite familiar. Familiar, yes, but apparently limestone is not exactly "unique" in it's sound absorption/reflection properties, is it?

Now, find the coefficients for granite and maybe you'll learn something (but I rather doubt it.)

H.

The above is an indication that you are unaware that the density and acoustical properties of stone always vary somewhat,

lol
what you just illustrated is everything has a different absorption reflection co efficient at the density boundry
which is what i said

reflection
Hypothetical Rock Properties
Rock VP, km/s ρ, kg/m3 V x ρ
Granite 5.0 2700 13,500
Basalt 5.5 3000 16,500
Limeston 6.0 2300 13,800
Sandstone 4.2 2500 10,500
Shale 2.5 2300 5,750

principles.ou.edu...
we are done here Harte

Danbones

The above is an indication that you are unaware that the density and acoustical properties of stone always vary somewhat,

lol
what you just illustrated is everything has a different absorption reflection co efficient at the density boundry
which is what i said

reflection
Hypothetical Rock Properties
Rock VP, km/s ρ, kg/m3 V x ρ
Granite 5.0 2700 13,500
Basalt 5.5 3000 16,500
Limeston 6.0 2300 13,800
Sandstone 4.2 2500 10,500
Shale 2.5 2300 5,750

principles.ou.edu...

Did you miss the term "hypothetical?"

I provided a link to a site with at least a dozen different limestones and their individual acoustic absorption coefficients (not shown in the list of properties you quoted above.)
I told you that acoustic absorption can vary greatly within the same bed of rock. You come back with amplitude ratios from reflections between two different rock beds.

There's a pic from your link that will serve to illustrate what I said so that perhaps you will understand it. It is a drawing labelled The Karcher Section. In it, you see a layer of shale overlaying a layer of limestone. The fact is, the acoustic absorption coefficient for the bed of shale will vary throughout that bed, and the acoustic absorption coefficient for the bed of limestone underneath will vary throughout that bed.

Now, suppose you show us what led you to claim that there was some sort of "unique" acoustic property to the limestone in the Hypogeum, and exactly how my data (the webpage you linked, actually) doesn't show that concrete (and brick, and marble) performs as well, or better than, limestone in this sound-reflecting property we're examining here? Keep in mind I've already shown a rather large variation in the acoustic absorption properties of different limestone beds with the link to the limestone site in my previous post.

Danbones
we are done here Harte

You were done several posts ago. You'r just getting dry and stringy now.

Harte

the whole seismographic industry turns on the different relections of sound waves
so lets have it your way for a second Harte
geologists don't exist

read em and weep Harte
yup, no such thing as seismic oil exploration
now don't be bitter

What types of surfaces reflect sound the best?
In: Sound Waves [Edit categories]
Answer:
We will find surfaces that are
hard and flat
to be the best reflectors of sound. To understand why, we need to review a couple of things about sound.

Sound is mechanical energy. The source of the sound will put the sound (mechanical) energy into the medium through which that sound is going to travel. This causes some movement in the medium through which the sound is propagating.

Surfaces that reflect sound best will not absorb the sound energy by moving. These surfaces will resist any movement and will thus not take any energy from the sound wave. This said, we'd expect a foam rubber wall will reflect far less sound energy than a concrete wall. Also, a wall that is flat will cause less scattering, which is a distributed redirection of the sound.

A flat wall will allow sound to be reflected directly back toward the source (for sound arriving at a right angle to the wall).

A wall that is made of cemented river stones, which are rounded, will scatter some of the sound energy and be less as good a reflector of that sound compared to a flat, smooth concrete wall.

wiki.answers.com...

hardness scales for granite and limestone and others

Granite
A popular choice and becoming a household standard, granite adds both beauty and value to your home. It’s a practical choice because of it’s natural strength, durability, and resistance to both heat and staining. Granite begins to melt around 1215 to 1260°C, so hot pans and pots are no threat and can be placed directly onto the granite countertop.

Granite is a hard rock sitting around a 6 or 7 on Moh’s scale of mineral hardness depending on the exact mix of minerals (quartz, feldspars, micas, and trace amounts of other minerals) making up a specific slab. This property makes granite difficult to scratch. And if scratching does occur, granite is one of the easiest rocks to fix.

Granite comes in literally thousands of colours and has a medium to coarse grain. This means all the different colours from the blend of minerals are easy to see.
Perfect for any room, granite can be used in fireplaces, countertops, bathtubs and showers, indoors, outdoors, and almost anywhere you can imagine.

Limestone
Limestone is a sedimentary rock formed from compressed calcium carbonate. Usually it forms underwater from the bones and shells of sea creatures as well as coral. Because of this, limestone may contain interesting fossils.

Limestone is even softer than marble. Sitting at 3 to 4 on the Mohs scale, simply scraping a copper penny against limestone can scratch its surface. However, scratches aren’t as visible in limestone as they are in marble.

Limestone comes in all sorts of earthy tones, from near-white and yellow-tan to dark grey and black. Like marble, it has a very high melting point making the stone ideal for limestone fireplaces and mantels.

stonemastergranite.com...

IN SUPPORT OF THE ABOVE POST


didn't Harte say there is no difference between working limestone over granite...?
i thought he said there was no difference they worked the limestone because it was there?

yet we have not only different hardnesses reflecting we have worked surfaces and textures
also soft copper can work limestone...

Should you, in the future, decide to respond to something I posted rather than inventing phrases and attributing them to me for the sole purpose of having something to argue against, I will be happy to respond.

Harte

reply to post by Harte


just askin if you said it Harte
can't you tell the difference?
pot calling the kettle black imho

Danbones
reply to post by Harte

 

just askin if you said it Harte
can't you tell the difference?
pot calling the kettle black imho

In fact, I said that, had the bedrock there been granite, you would find the sound reflections going on there to be the same. I added that, if it was Granite, they probably wouldn't have dug it out like they did.

I also stated that granite (and any other hard stone - not pumice, for example) reflects sound as well or better than limestone. This fact is attested to in the quote you recently provided, given the hardness of granite vs. limestone.

Harte

The Greeks probably used limestone because it's easy to both find, quarry and shape.

Please elucidate for us the acoustic properties of limestone that are not matched by other stones. And I don't mean the acoustic properties wherein limestone transfers sound waves through a limestone bed. I mean the property you state that it reflects sound better than, say, granite or, say gneiss or any of the various feldspars.

here is the quote Harte
i asked above because i figured you'd clarify
i have more important things to do at this time then prove that oil geoligists exist over and over again

why don't you start a thread on your views Harte instead of fixating on points that have been made over and over again
like from your quote above
BTS plainly quoted the experts opinion of the limestone seats and you just went on and on about absorbtion ( vs reflection) when any engineer would know its a ratio

and again oil geologists use SOUND seismic waves to detect all the different types of rock via that ratio

Danbones

The Greeks probably used limestone because it's easy to both find, quarry and shape.

Please elucidate for us the acoustic properties of limestone that are not matched by other stones. And I don't mean the acoustic properties wherein limestone transfers sound waves through a limestone bed. I mean the property you state that it reflects sound better than, say, granite or, say gneiss or any of the various feldspars.

here is the quote Harte
i asked above because i figured you'd clarify
i have more important things to do at this time then prove that oil geoligists exist over and over again

why don't you start a thread on your views Harte instead of fixating on points that have been made over and over again
like from your quote above
BTS plainly quoted the experts opinion of the limestone seats and you just went on and on about absorbtion ( vs reflection) when any engineer would know its a ratio

and again oil geologists use SOUND seismic waves to detect all the different types of rock via that ratio

edit on Monam3b20143America/Chicago35 by Danbones because: (no reason given)

edit on Monam3b20143America/Chicago40 by Danbones because: (no reason given)

Yes, they do. I merely pointed out that the ratios given in your table are not the same as the absorption coefficients we were using to compare stones and how much sound they reflect.

If you wish to use the "hypothetical" table you posted, then I would note that, according to the values in that table, granite reflects sound better than limestone.

But, like I said, limestone is easier to carve.
The post I was responding to, in the quote you provided, was as follows:

burntheships
Acoustic properties of limestone

Limestone has particular acoustic properties.
The Greeks chose limestone to line the seats in
their amphitheaters because of its ability to transfer the sound.

Where did they get this information?

I note that neither burntheships nor you have provided any information as to these "particular" and "unique" sound-reflecting and sound-transferring properties limestone possesses.

You seem to think that, because geologists often use sound to see underground, that is somehow supportive of the idea that limestone has some special acoustical property with regard to reflecting sound.

I'm still curious as to what was meant in the post from burntheships.

Harte

hi Harte

I realize that if you are a mechanical engineer, you worked very hard to get there, you are a very precise person, and you are probably very good at math.
Math is NOT my strong point, my ears are my strong point...(and my song writing apparently , i get paid for that too)

I get paid because i know what sounds nice to the ear and what does not, what moves people and what does not, and how to achieve that...i compete with engineers but i learned by putting thousands of hours on the job, but i don't call myself an engineer..even though i get listed as one..like a train engineer..i am a very specialized operator...
i joke about being an injun-ear

that said:

i will admit the difference in rock types is subtle, but the brain is subtle too

I would think that the important and interesting thing about these types of places is the whole "who what where and why and how" of the whole place and the culture, and the history, ?

so after this post win lose or draw, i am moving on..if thats conceding; fine, readers will decide what ever they want to.


why mention siesmic geology?
Because siesmic soundwaves are returned to the reciever and by the sound prints of the different rocks the different strata are identified...reflection/absorpsion for identification, as the diagram i posted earlier illustrates.

As a sound technician with a computer, i can sample at 196,000 samples per second at 24 bit resolution. I can tell you what your strings are made of, what metal your instruments are made of...the HARMONIC content is totally unique for everything..
The brain can hear the difference between that 196,000 samples per second and analogue sound though
thats how precise the human system is....

If you don't get this post, then i'm just going to concede this tiny point, and i am going to move on because there is to much of interest on this subject for me to hang on this minute point too much longer
no offence ment...its taking the fun out of it for me

and BTS is not me, so you would have to get any clarification from her, if required
i hang out on her threads because she is one of the classiest posters on ATS and she is a most gracious thread host, and she pics such interesting topics...

here, i can't explain the way sound is used in geological exploration any better then this:

GEOPHYSICAL SURVEYS

Geophysical techniques used for petroleum exploration utilize equipment to measure such things as: electrical currents, gravitational and magnetic anomalies, heat flow, geochemical relationships, and density variations from deep within the earth. Each technique records a different set of characteristics which can be used to locate hydrocarbons beneath the surface of the earth.

Seismic surveys use vibration (induced by an explosive charge or sound generating equipment) to provide a picture of subterranean rock formations at depth, often as deep as 30,000 feet below ground level (BGL). This is accomplished by generating sound waves downward into the earth's crust which reflect off various boundaries between different rock strata. On land, the sound waves are generated by small explosive charges embedded in the ground or by vibrator trucks, sometimes referred to as thumpers which shake the ground with hydraulically driven metal pads. The human ear can barely hear the thump, but the frequency generated penetrates the earth's crust. The echoes are detected by electronic devices called geophones which receive the reflected sound waves and the data are recorded on magnetic tape which is printed to produce a two-dimensional graphic illustrating the subsurface geology.

Offshore surveys are conducted in a slightly different manner. Boats tow cables containing hydrophones in the water, which is similar to geophones on land. Sound waves use to be created by dynamite, but this method killed a variety of sea life. The most acceptable method today is to generate sound waves using pulses of compressed air which creates large bubbles that burst beneath the water surface creating sound. The sound waves travel down to the sea floor, penetrate the rocks beneath, and return to the surface where they are intercepted by the hydrophones. Processing and illustration is the same as the dry land method.

In this type of survey, sound waves are sent into the earth where they are reflected by the different layers of rock. The time taken for them to return to the surface is measured as a function of time. This measurement reveals how deep the reflecting layers are; the greater the time interval, the deeper the rock layer. Moreover, this technique also can determine what type of rock is present because different rocks transmit sound waves differently.

The most sophisticated seismic surveys are three-dimensional (3-D). The recorded data is processed by computer and the results are a detailed, 3-D picture of the formations and structures below the surface. The process is expensive, on the order of $30,000 per mile

dnr.louisiana.gov...

as i stated before regarding the difference in hardness between limestome and granite:

In ancient Egyptian art no representations have been found of the sawing of stone by means of a copper blade and an abrasive nor has any lapidary slabing saws been found in the archaeological record (...

www.oocities.org...

so
they had to tune those surfaces and they had what for tool metal?
copper...and abrasives...maybe a simple acid...? wedges hammers, dolorite
too early for alloys i think.... middle kingdom ... first alloys .2050 BC and 1650 BC..
hypogeum....3300-3000 BC

Early ancient Egyptian lapidary slabbing saws would have been made of copper, either cast or cold-worked until the Middle Kingdom,

from the above link

now the egyptians did cut granite with copper it says, but they prefered limestone in the early dynasties
it says it rright there...was sound a big deal...maybe or maybe not, but there is no accounting for taste as they say...

Third through Fifth Dynasties
During the earliest period, pyramids were constructed wholly of stone. Locally quarried limestone was the material of choice for the main body of these pyramids, while a higher quality of limestone quarried at Tura (near modern Cairo) was used as the outer casing. Granite, quarried near Aswan, was used to construct some architectural elements, including the portcullis (a type of gate) and the roofs and walls of the burial chamber. Occasionally, granite was used in the outer casing as well, such as in the Pyramid of Menkaure

www.oocities.org...

now the clincher
porosity:

Granite has a porosity ratio of between 0.4% – 1.5%
Limestone has a porosity ratio of between 0.6% – 31%
Absorption
A stone's level of porosity and permeability will determine how absorbent it is.

www.ethosmarblecare.co.uk...
we saw the definition of absorption above

there
if any readers want to decide to star this post, great.
if you think Harte is correct by all means star what ever post you feel expresses his views the best...

that as fair as i can think of considering....

now, we return you to the regularly scheduled hot dancing girls and ice cold beers

I also stated that granite (and any other hard stone - not pumice, for example) reflects sound as well or better than limestone. This fact is attested to in the quote you recently provided, given the hardness of granite vs. limestone.

Harte, you just admitted there is a difference in sound quality between granite and limestone.
i said the quality of sound is different, between granite and limestone, and i mentioned that limestone was chosen for its sound qualities, quote me if im mistake here but i don't recall ever saying limestone was a better reflecter

thats what we have been arguing about all this time?

heh heh lol
come on now, you have to admit that thats funny
we have been arguing all this time for nothing


ill say one thing you are one tough debater
next time lets make thesis statments BEFORE WE START

Danbones

I also stated that granite (and any other hard stone - not pumice, for example) reflects sound as well or better than limestone. This fact is attested to in the quote you recently provided, given the hardness of granite vs. limestone.

Harte, you just admitted there is a difference in sound quality between granite and limestone.
i said the quality of sound is different, between granite and limestone, and i mentioned that limestone was chosen for its sound qualities, quote me if im mistake here but i don't recall ever saying limestone was a better reflecter

You agree that the sound in the hypogeum is reflected sound, right?

So, as I asked in my first post in this thread, what are these acoustic properties possessed by limestone that the bolded portion I quoted above refer to?

I have stated many times that other stones reflect sound as well as, or better than, limestone.

I've also stated that the reason the Hypogeum is excavated in limestone is that limestone is present under the ground at the site of the Hypogeum. It is possible that the site was selected for this reason, since limestone is reasonably easy to cut and carve. It certainly wasn't chosen for any acoustic property limestone possesses.


Harte