Monday 2 April 2012

Are blind tests bogus? Examples of blind tests with positive results.

Some claim that blind tests are bogus because they are designed to create a fail or cannot be passed and they involve trickery or deception.

I do not think that is true because

- they can be passed, such as blind tests of speakers and bit rates. Use the same test with cables and the result is a fail. That is because there is no difference between cables, but there is one between speakers and bit rates. If the test was itself designed to fail, then why not fail with speakers?

- I do not like the blind tests that have been done where people are told they are listening to different cables, but in fact there has been no change. It is interesting, but again a bit dubious when something like a wire coat hanger is slipped into a cable test without anyone's knowledge. My preference is the simple two cables, let the subject see and hear both in action. Then once blinded use one and then say, 'I am may or may not change to the other cables now, please say if you can hear a difference or not?' Then repeat that for about 20 times. Where is the deception in that?

You can also decide if you do have 'golden ears' here

http://www.audiocheck.net/blindtests_index.php

So here are blind tests that have positive results where people could hear a difference.

1 - A blind test of speakers, passed by the subject. Interestingly, the subject failed to identify different crossovers, one more expensive than the other.

http://www.audioholics.com/news/editorials/axiom-blind-listening-test

2 - One of amps with 500 participants EDIT - it is debatable whether this is actually a pass or not.

http://www.stereophile.com/features/113/index.html

3 - Power amp blind tests, two of which are positive.

http://home.provide.net/~djcarlst/abx_data.htm

4 - Head-Fi, by member Pio2001 between a Marantz integrated amp and Pro-ject Headphone amp

http://www.head-fi.org/forum/thread/429619/headphone-outputs-lots-of-measurments-and-one-abx

5 - An interesting Boston Audio Society article about two tests. The tweaked CD test is a fail, but read on and an amplifier blind test is a pass.

http://www.bostonaudiosociety.org/bas_speaker/wishful_thinking.htm

6 - A Hydrogen Audio test of different gauge speaker cables.

http://www.hydrogenaudio.org/forums/index.php?showtopic=14082&st=25

7 - PSB speaker blind test, the top of the range speaker won

screenOvenNRC.jpg

http://www.psbspeakers.com/audio-topics/Birthplace-of-Good-Sound

8 - ABX Comparator. A series of blind tests of different kit and cables.

Starting with the cables, differences were found with video cables over very long runs of 100 feet in comparison to a 6 foot one.

http://home.provide.net/~djcarlst/abx_vid.htm

Then interconnect and speaker cables, five tests and no differences found.

http://home.provide.net/~djcarlst/abx_wire.htm

A speaker test with a very large sample found 97% could tell the difference

http://home.provide.net/~djcarlst/abx_spk.htm

CDPs and a DAC did less well

http://home.provide.net/~djcarlst/abx_cd.htm

Power amps did a bit better

http://home.provide.net/~djcarlst/abx_pwr.htm

But what was very noticeable was the likes of distortion, filters and a small change in volume

http://home.provide.net/~djcarlst/abx_data.htm

9 - Matrix Hifi between two amps where two testers got all 30 tests correct, 60 attempts in all (in Spanish, Google translator used)

http://translate.google.com/translate?js=n&prev=_t&hl=en&ie=UTF-8&layout=2&eotf=1&sl=es&tl=en&u=http%3A%2F%2Fwww.matrixhifi.com%2Fcontenedor_trivsclat.htm&act=url

10 - 16bit vs 24bit, Gearslutz.com forum, 9 out 10 correctly identified

http://www.gearslutz.com/board/so-much-gear-so-little-time/358301-24-vs-16-bit-not-audible.html

11. Sampling rate, 44.2kHz vs 88.2 kHz, AES May 2010

http://www.aes.org/e-lib/browse.cfm?elib=15398

Thursday 23 February 2012

Hifi Miscellany

Testing Sites

Tom Nousaine's test site

http://www.nousaine.com/nousaine_tech_articles.html

Ethan Winer's test site

 http://www.ethanwiner.com/index.htm


NwAvGuy's test site/blog

http://nwavguy.blogspot.com/


The Audio Critic, critical writing and testing of hifi

http://www.theaudiocritic.com/

General bibliography of hifi testing

http://www.geocities.ws/jonrisch/c4.htm


Audibility

Audiocheck, check out your hearing and see what really is audible

http://www.audiocheck.net//

What can we hear?

http://www.silcom.com/~aludwig/EARS.htm#Subjective_vs_objective

Listening test of distortion

http://www.klippel.de/listeningtest/lt/


Jitter

http://aoselectronics.com/jitter_article.html

Testing of audibility of distortion caused by jitter

http://www.jstage.jst.go.jp/article/ast/26/1/50/_pdf

The Audio Critic on jitter

http://www.theaudiocritic.com/back_issues/The_Audio_Critic_21_r.pdf

BBC Report on jitter

http://downloads.bbc.co.uk/rd/pubs/reports/1974-11.pdf

TNT audio on what is jitter?

http://www.tnt-audio.com/clinica/jitter1_e.html

Hydrogen Audio forum and a thread about the audibility og jitter

http://www.hydrogenaudio.org/forums/index.php?showtopic=51322&st=25


Benchmark Audio and their claims about jitter

http://www.benchmarkmedia.com/appnotes-d/jittercu

Stereophile and their claims about jitter

http://www.stereophile.com/reference/1093jitter/#



Testing of claims about cables

St Andrews Uni, testing skin effect

http://www.st-andrews.ac.uk/~www_pa/Scots_Guide/audio/skineffect/page1.html


HDMI

C-net on there being no difference between HDMI cables

http://news.cnet.com/8301-17938_105-20056502-1/why-all-hdmi-cables-are-the-same/

Test of HDMI cables

http://www.expertreviews.co.uk/home-entertainment/1282699/hdmi-investigated-are-expensive-cables-a-scam/3

Another test with video games

http://www.eurogamer.net/articles/digitalfoundry-vs-hdmi

One with lots of cables

http://www.audioholics.com/education/cables/long-hdmi-cable-bench-tests/hdmi-cable-testing-results


ABX testing

http://www.hopkins-research.com/abx.htm


Tests of cables

http://sfguitarworks.com/?p=1521


Spurious cable compnay claims

Atlas on directionality  http://www.atlascables.com/fine-tuning.html

Sunday 15 January 2012

Self defence with a gun - how much is a myth?

This is from a discussion with fellow sceptics about the prevelance of guns in the US and the right to bear arms.

Defensive gun use (DGU) is often cited as a reason to have gun at home or on your person. So being a sceptic I went to have a look at how many times DGUs have taken place and to what extent DGUs are a good reason to have a gun.

One side claims many succesful uses of self defence. For example, from the St Louise University Public Law Review in 1999, "Guns and Justifiable Homicide"

http://saf.org/LawReviews/SouthwickJr1.htm

"However, if each execution and each justifiable homicide results in 7.5 fewer murders, the total of 697 justifiable homicides each year should have deterred over 5,200 murders each year. Compared with the approximately 21,500 [Page 221] murders actually occurring each year as shown in Table 2,[17] this implies that the murder rate would have been about 24 percent higher without these justifiable homicides. The civilian justifiable homicides averaged 299 per year, which should have saved over 2,200 murders per year."

That is very speculative and indeed the author admits "Of course, the above argument relies on some very strong inferences which may not be valid."

The other side, such as The Harvard School of Public Health disagrees with the above

http://www.hsph.harvard.edu/research/hi ... index.html

and states

"We then try to validate the claims of many millions of annual self-defense uses against available evidence.
Major findings: The claim of many millions of annual self-defense gun uses by American citizens appears to be invalid."

"We analyzed data from two national random-digit-dial surveys conducted under the auspices of the Harvard Injury Control Research Center.
Major findings: Criminal court judges who read the self-reported accounts of the purported self-defense gun use rated a majority as being illegal, even assuming that the respondent had a permit to own and to carry a gun, and that the respondent had described the event honestly from his own perspective."

"Using data from a national random-digit-dial telephone survey conducted under the direction of the Harvard Injury Control Research Center, we investigated how and when guns are used in the home.
Major findings: Guns in the home are probably used more often to frighten intimates than to thwart crime; other weapons are far more commonly used against intruders than are guns."

Then from this study

http://www.pulpless.com/gunclock/kleck2.html

"There has probably been more outright dishonesty in addressing the issue of the frequency of defensive gun use than any other issue in the gun control debate."

So which side is correct and how much of self defence with a gun is a myth?

I was given various stories from the US press about DGUs, but what was in the back of my mind was 'was it really a DGU, or was it someone in a panic brandishing or firing their gun in what does not amount to self defence?'

Here are a whole host of examples how self defence ended up in unnecessary deaths and injuries

http://www.cato.org/raidmap/

They are reports of deaths of people and police during no knock warrant entries to houses. The blame is laid in the article on the warrant, but it is really the use of guns that has caused the deaths and injuries. The red, blue and black icons show times where self defence was not against a criminal attack but the police.

In Scotland this incident was widley reported and caused revulsion against the attitude of Americans and DGUs. It is an example of supposed self defence which seriously calls into question what passes for self defence in the US

http://www.independent.co.uk/news/uk/fa ... 99010.html


"Mr De Vries, 29, from Aberdeen, was shot at about 5am local time after he knocked on the back door of a house, (in Houston, Texas) apparently seeking a taxi for himself and a Scottish colleague, Sydney Graves, 42.

Relatives were angered by a newspaper photograph of the scene, which they said seemed to show the door was glass-panelled. This suggested that Mr De Vries would have been visible to the man who fired several shots through the door."

Surely there will be records kept on DGUs? The answer is to my mind surprising and it is 'NO'.

Many articles about DGUs cite the follwing study by Gary Kleck and Marc Gertz from the Northwestern University School of Law in 1995.

http://www.guncite.com/gcdgklec.html

There is a lot of guestimation going on, too much for my liking to get an accurate picture of what is going on. Is there any enquiry made to see if a DGU really is self defence or not?

Surely such records would provide a far more accurate picture of DGUs and from that you would know how often such takes palce and how often they really are defensive and prevented a crime. From that study, which was a teleephone survey -

 "Are these estimates plausible? Could it really be true that Americans use guns for self-protection as often as 2.1 to 2.5 million times a year?"

It does seem a lot, but it does include just having a gun to scare away someone and not just shooting people.

"How could such a serious thing happen so often without becoming common knowledge? This phenomenon, regardless of how widespread it really is, is largely an invisible one as far as governmental statistics are concerned. Neither the defender/victim nor the criminal ordinarily has much incentive to report this sort of event to the police, and either or both often have strong reasons not to do so. Consequently many of these incidents never come to the attention of the police, while others may be reported but without victims mentioning their use of a gun. And even when a DGU is reported, it will not necessarily be recorded by the police, who ordinarily do not keep statistics on matters other than DGUs resulting in a death, since police record-keeping is largely confined to information helpful in apprehending perpetrators and making a legal case for convicting them. Because such statistics are not kept, we cannot even be certain that a large number of DGUs are not reported to the police.

The health system cannot shed much light on this phenomenon either, since very few of these incidents involve injuries.[61] In the rare case where someone is hurt, it is usually the criminal, who is unlikely to seek medical attention for any but the most life-threatening gunshot wounds, as this would ordinarily result in a police interrogation. Physicians in many states are required by law to report treatment of gunshot wounds to the police, making it necessary for medically treated criminals to explain to police how they received their wounds."

So we apparently get huge official under reporting and no official records. So really we have little idea as to what is really going on, we do have to estimate.

The survey's sample size;

"A total of 222 sample cases of DGUs against humans were obtained. For nine of these, the R broke off discussion of the incident before any significant amount of detail could be obtained, other than that the use was against a human. This left 213 cases with fairly complete information. Although this dataset constitutes the most detailed body of information available on DGU, the sample size is nevertheless fairly modest. While estimates of DGU frequency are reliable because they are based on a very large sample of 4,977 cases, results pertaining to the details of DGU incidents are based on 213 or fewer sample cases, and readers should treat these results with appropriate caution. "

An example of the questions asked

"We asked Rs: "If you had not used a gun for protection in this incident, how likely do you think it is that you or someone else would have been killed? Would you say almost certainly not, probably not, might have, probably would have, or almost certainly would have been killed?" Panel K indicates that 15.7% of the Rs stated that they or someone else "almost certainly would have" been killed, with another 14.2% responding "probably would have" and 16.2% responding "might have."[96] Thus, nearly half claimed that they perceived some significant chance of someone being killed in the incident if they had not used a gun defensively."

I am sorry, but I am very sceptical of that survey primarily because it a survey of perception and not it is not an examination of facts.

It also makes no effort to find negative results. Does anyone expect a respondant o say, my DGU was inappropriate, I got it wrong, I never should have used my gun? 

I have since found a study of American DGUs from Australia of all places, by a Tim Lambert of the University of South Wales

http://www.cse.unsw.edu.au/~lambert/guns/lott/lott.pdf

It has some official data from Dade County in Florida on DGUs

"There is empirical data on how often permit holders use their weapons:
Dade county police kept records of all arrest and non-arrest incidents
involving permit holders in Dade county over a 5 year period [8]. Lott cites
this study to show that gun misuse by permit holders is extremely rare (page
11):
A statewide breakdown on the nature of those crimes is not available,
but Dade county records indicate that four crimes involving
a permitted handgun took place there between September 1987
and August 1992
and none of those cases resulted in injury.
Lott fails to note that the same study shows that defensive gun use by
permit holders is also extremely rare (page 692 of [8]):
The Dade police recorded the following incidents involving the
defensive use of licensed carry firearms: two robbery cases in
which the permit-holder produced a firearm and the robbers fled,
two cases involving permit-holders who unsuccessfully attempted
to stop and apprehend robbers (no one was hurt), one robbery
victim whose gun was taken away by the robber, a victim who
shot an attacking pit bull; two captures of burglars, three scaring
off of burglars, one thwarted rape, and a bail bondsman firing
two shots at a fleeing bond-jumper who was wanted for armed
robbery.
There were only 12 incidents where a criminal encountered an armed
permit holder.


Twelve in 5 years and some DGUs were unsuccessful and I would not say the bail bondsman was acting in self defence at all. A bit further on and

"Kleck’s survey [22] indicates that 64% of defensive gun uses are reported to the police." So that means if all DGUs (using Kleck's own method of extrapolation) were reported there were 19 DGUs in Dade County over five years. But this is the Gary Kleck who is widly cited for his claim that guns were used for self defence about 2.5 million times a year or once every thirteen seconds.

http://actionamerica.org/guns/sdcnt-wdgt.shtml

Lambert concludes

"If you believe Kleck’s survey of defensive gun use [21] there were at least
100,000 DGUs (defensive gun uses) in Dade county over the five year period.
If you believe the NCVS [40] there were at least 2,500. Either way, the 12
by permit holders makes no significant difference to the total"


That is a massive variation, so much so either the official records are way out or the academic study is, or maybe both?

But returning to a Harvard study by David Hemenway

http://www.stat.duke.edu/~dalene/chance/chanceweb/103.myth0.pdf

if you submit examples of DGUs for legal examination, many are not self defence at all.

A study of DGUs using a sample period from newspaper articles, Denton & Fabricus 2004 Arizona State University

http://www.ncbi.nlm.nih.gov/pmc/article ... p00096.pdf

It finds significantly lower results of the Kleck and Gertz telephone survey

"Conclusions: These findings cast doubt on rates of DGUs reported in an influential study by Kleck and
Gertz, which predict that the police should have known about 98 DGU killings or woundings and 236
DGU firings at adversaries during the time the newspaper was surveyed. The findings reported here were
closer to predictions based on the National Crime Victimization Survey, which suggest that the police
should have known about eight DGU killings or woundings and 19 DGU firings at adversaries."

But, there is surely as little chance of getting a true figure using newspaper reports than with a telephone survey? That is shown here in various responses to the study

http://injuryprevention.bmj.com/content ... prev_el_68

Not that that survey is quoted anywhere else that I can find. The pro gun side quote Kleck and Gertz almost exclusively, after all, it has by far the highest use of DGUs suggesting guns are needed for self defence on a massive scale.

There is one survey that found an even higher rate of DGUs, this survey (the NSPOF) from the National Institute of Justice in 1997 by Cook and Ludwig

http://www.tscm.com/165476.pdf

But I suspect it not used by the pro-gun lobby as it casts doubts on its own survey results which came up with 23 million DGUs in 1994. There were 45 respondants who stated they had had a DGU and one of them claimed 52 DGUs that year. Even applying Kleck and Gertz's means of identifying real DGUs drops the number to a still very high 4.5 million uses.

So the NSPOF is concerned about false positives as

"NSPOF estimates also suggest that
130,000 criminals are wounded or
killed by civilian gun defenders. That
number also appears completely out of
line with other, more reliable statistics
on the number of gunshot cases (at hospitals)"

"Some troubling comparisons. If
the DGU numbers are in the right
ballpark, millions of attempted assaults,
thefts, and break-ins were
foiled by armed citizens during the 12-
month period. According to these results,
guns are used far more often to
defend against crime than to perpetrate
crime. (Firearms were used by
perpetrators in 1.07 million incidents
of violent crime in 1994, according to
NCVS data.)"

The survey sums up its doubts about its own results

"...... people who draw their guns to defend themselves against perceived threats are not necessarily innocent victims; they may have started fights themselves or they may simply be mistaken about whether the other persons really intended to harm them."

The academics involved in the study of guns and self defence are a very argumentative bunch. Here is David Hemenway's critique of Jongyeon Tark & Gery Kleck 2004 study "Resisting Crime: The Effects of Victim Action on the Outcomes of Crimes."

http://www.hsph.harvard.edu/faculty/Hem ... ments.html

Hemenway uses Tark and Klecks own statistics to point out

"First, respondents were injured in 26.4% of the incidents in which they used some form of resistance; when they did nothing, they were injured 18.5% of the time"

"They compare one form of resistance–calling the police or guard–with the other 15 forms (e.g. attacked with gun; threatened with gun, attacked with nongun weapon; struggled; chased offender; yelled; stalled; argued; ran away; screamed) in terms of the likelihood of receiving an injury AFTER taking this mode of resistance. In simple comparisons, nothing is better than calling the police–only 0.9% of the time did this lead to injury. Threatening with a gun is followed by an injury 2.5% of the time; yelling 2.7%; attacking without a weapon 3.8%; struggling 4.1%; and the highest, stalling 4.5%"

"In multivariate analysis, only "ran away, hid" is significantly better than calling the police or guard in terms of not receiving an injury"

So despite various claims in this thread about the ineffectiveness of calling the police it is the second best way of not being injured. The most effective way is my repeated suggestion in this thread of running away. Instead of guns, it would appear you should plan escape routes, have hidy holes and indeed something I think is really cool is get a panic room.

There is further doubt cast on Gary Kleck's belief that DGUs are commonplace. Here are his statistics regarding defense during crimes

http://www.hsph.harvard.edu/faculty/Hem ... ments.html

".... for sexual assaults, only 1 victim in 1,119 total incidents reported attacking or threatening with a gun (15 used a nongun weapon; 38 called the police or guard; 120 attacked without a weapon; 161 ran away; 219 yelled; 343 struggled). In robberies 1.2% of victims used a gun, whereas 3.8% called the police or guard, 12.7% ran away, and 20.5% struggled. In all confrontational crimes, 0.9% of victims reported using a gun, 1.7% used a nongun weapon, 7.2% called the police, 10.1% ran away, 13.8% struggled, and 29.3% did nothing."

So where are the millions of DGUs? Only a tiny percentage of crimes involve a DGU. Then we have to consider how appropriate the DGU was and if it really was self defence.

Indeed looking closer at supposed DGUs finds instances of vigilateism and outright murder

 Here is vigilanteism dressed as self defence

http://en.wikipedia.org/wiki/Joe_Horn_s ... ontroversy

"One vital piece of evidence were segments of Mr. Horn’s 9-1-1 calls which could have possibly incriminated Mr. Horn or shown his innocence. The most scrutinized segment is presented below:

Joe Horn: “I’ve got a shotgun; do you want me to stop them?”

The Pasadena emergency operator responded: “Nope. Don’t do that. Ain’t no property worth shooting somebody over, O.K.?”

Mr. Horn said: “But hurry up, man. Catch these guys will you? Cause, I ain’t going to let them go.”

Mr. Horn then said he would get his shotgun.

The operator said, “No, no.” But Mr. Horn said: “I can’t take a chance of getting killed over this, O.K.? I’m going to shoot.”

The operator told him not to go out with a gun because officers would be arriving.

“O.K.,” Mr. Horn said. “But I have a right to protect myself too, sir,” adding, “The laws have been changed in this country since September the first, and you know it.”

The operator said, “You’re going to get yourself shot.” But Mr. Horn replied, “You want to make a bet? I’m going to kill them.”

Moments later he said, “Well here it goes, buddy. You hear the shotgun clicking and I’m going.”

Then he said: “Move, you’re dead.”

There were two quick gunshots, then a third.

“I had no choice,” Mr. Horn said when he got back on the line with the dispatcher. “They came in the front yard with me, man.”

The 9-1-1 call ended about 80 seconds after the shots were fired, when officers arrived on the scene."

So they moved and now they are dead. If the state does not execute people for theft, why should some people think they can execute other people for theft? The shooter had a very clear choice, wait for the police to arrive. But his blood lust got the better of him. He was desparate to go and kill. It is not as if he resorted to shouting at them or even a warning shot. Move your dead, bang, end.

 Here is another alleged DGU which happens if you call at the wrong house during Halloween dressed as John Travolta

http://en.wikipedia.org/wiki/Yoshihiro_Hattori

"District Attorney Doug Moreau concentrated on establishing that it had not been reasonable for Peairs, a 6-foot-2, well-armed man, to be so fearful of a polite, friendly, unarmed, 130-pound boy, who rang the doorbell, even if he walked toward him unexpectedly in the driveway, and that Peairs was not justified in using deadly force. Moreau stated, "It started with the ringing of the doorbell. No masks, no disguises. People ringing doorbells are not attempting to make unlawful entry. They didn't walk to the back yard, they didn't start peeking in the windows."

"You were safe and secure, weren't you?" Moreau asked Peairs during his appearance before the grand jury. "But you didn't call the police, did you?"
"No sir." Peairs said.
"Did you hear anyone trying to break in the front door?"
"No sir."
"Did you hear anyone trying to break in the carport door?"
"No sir."
"And you were standing right there at the door, weren't you - with a big gun?"
Peairs nodded.
"I know you're sorry you killed him. You are sorry, aren't you?"
"Yes sir."
"But you did kill him, didn't you?"
"Yes sir."

But he was aquitted much to the horror of Japan, who like the British see such actions as a vigilante summary execution disguised as a right.

Further doubt about the number of DGUs comes here

http://propagandaprofessor.net/2012/02/18/estimating-defensive-gun-uses-reasonably/

"FBI statistics show that for the five-year period ending in 2010, there was an average of 213 justifiable homicides per year by firearm. (A justifiable homicide is not necessarily a defensive use, but the vast majority of them fit the description.) The Kleck-Gertz figures indicate that the defenders wound or kill their assailants only 8.3 percent of the time, but this is surely far too low – especially given that many alleged defensive gun uses involve nothing more than mentioning the existence of a gun! And the figures don’t specify how many are fatal. But if indeed there are 2.5 million DGUs per year, then the fatal shootings would account for only .0085 percent!  So let’s just skip Kleck altogether and stick with real numbers."

Then there is the case of Marissa Anderson who was jailed for not killing her assailant. Instead she fired a warning shot into the ceiling of her house. That worked as her assailant ran off, alive. But by not killing him she is now in prison for assault with a deadly weapon.

Marissa-Alexander-shoot-to-kill-or-you-must-not-be-scared-enough/

How do you square Kleck and Gertz with Marissa Anderson? Either there should be millions of dead killed in self defence, or millions in prison for assault with a deadly weapon as they chose not to kill. 


CONCLUSION

 I suspect the truth is somewhere in the middle, but no one will ever get a really accurate figure. The issue is further clouded by what is supposed to pass as a DGU, which if you leave it to a survey respondant is very inaccurate. Closer study of claimed DGUs and most are not.

It is not really known how many DGUs there are in the US. Pro-gun lobbyists use the highest figures that they can find, figures that are so high and when examined in more detail are found to contain a lot of guessing and cases where the use of the gun was not self-defence at all.


SOURCES

Tim Lambert Report 2004

Denton & Fabricius Report

Cook & Ludwig Report

Harvard School of PH - Study of DGUs

David Hemenway Harvard School of Public Health

David Hemenway Report

Hemenway on Kleck & Tark

The Lott Report

Defensive Use of Firearms 1987-90

Violence Policy Centre

Southwick Report

Kleck and Gertz Report

Kleck - Guns and self defence

Kleck on the Branas Report

Gun Owners of America Fact Sheet

Guncite.com general link