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Aug-24-03, 08:26 PM (EST)
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"Audio Analysis of the 911 Call"
   Audio Analysis of the 911 Call
of Patsy Ramsey

20 August 2003, 24 August 2003

"Dave" on Jameson's Webbsleuths (www.webbsleuths.com)


Copies of the recording of the emergency 911 call made by Patsy Ramsey were analyzed using audio software; results are discussed. It is concluded that purported conversation between the Ramseys is a combination of several different noise sources that give only the appearance of conversation. MP3® files have been produced which demonstrate both spectral differences between noise sources and the similarity between different sections of the recordings in terms of timing and cadence, suggesting a repetitive, mechanical source for some of the sources.


On 26 December 1996, Patsy Ramsey, then of Boulder, Colorado, made a 911 emergency call to the Boulder Regional Communication Center to report the kidnapping of her daughter, JonBenét. The 911 call was recorded, and very recently (July 2003) the Boulder County District Attorney's office has released audio copies of Patsy Ramsey's 911 call in the form of audio cassette tapes and audio CD's.

A controversy has existed ever since 1997 as to whether or not the recording of the 911 call contains unintentionally overheard conversation between members of the Ramsey family after the point where it was assumed that Patsy had hung up the phone. Some of those investigating the case of the murder of six-year-old JonBenét Ramsey seem to think that this issue is a very important one while others believe that regardless of what is on the tape, it is of very little evidentiary value, unless it is a confession of some sort. The main issue appears to be whether or not Burke Ramsey, JonBenét's older brother, was awake at the time of the 911 call. The Ramseys had maintained that Burke was asleep at this time while certain investigators had maintained that he was awake and speaking with his parents, therefore that the elder Ramseys engaged in some sort of deception, so perhaps lied about the circumstances surrounding the death of their daughter.

This report contains a technical discussion of testing that was done on both an audio cassette recording and an audio CD that were obtained from the Boulder County DA's office. The audio cassette and CD track are described, various types of processing are discussed, including separate processing and testing of portions of the recordings that some believe to be conversation. The conclusion is reached that these purported conversations are almost certainly not actually conversation by the Ramseys which is being picked up over their phone line and recorded after Patsy thought she had hung up the phone. If there is such conversation during the controversial audio sections, it is not audible even after various types of enhancement. Instead it appears that different types of noise with different spectral characteristics are superimposed in such a manner as to produce the appearance of voices. The appearance of voices would no doubt be especially strong in the presence of imagination empowered by suggestion and wishful thinking.

Audio Processing

A cassette tape and an audio CD of the emergency 911 call made by Patsy Ramsey on 26 December 1996 were obtained from the Boulder County District Attorney's office in Boulder, Colorado. For a more complete description of the audio processing steps applied, please refer to the Appendix. What follows here is a summary in text form, but is still intended primarily for a technical audience.

The "tape" was a recording on a common-usage, 120-minute audio cassette, a Maxell® UR, normal-bias tape. This tape was played on a Pioneer® CW-650R dual-cassette tape deck. A digitized version was produced by feeding the output of the tape deck into a Behringer® Eurorack MX802A mixer, the output of which was fed into a Terratech EWX-2496 mastering sound card that was installed in a Pentium III® computer. The recording software was Steinberg® WaveLab(tm) Lite, set for monophonic recording, 24-bit, 96,000 samples per second.

The "CD track" was a single audio track on a generic, brandless CD-R or CD-RW, probably CD-R. The track data were so-called CD quality or 16-bit, 44,100 samples per second, stereo (actually dual monophonic). The audio track was ripped from the CD track using Ahead's Nero® CD burning software that was bundled with a Creative Labs® 8432E CD/RW CD burner, reportedly a relabeled Plextor®. The stereo image was discovered to be two completely identical monophonic tracks. The left channel of the CD track was then upsampled to a monophonic, 24-bit, 96,000 samples per second WAV file using Syntrillium's CoolEdit® 2000.

Both the tape and the upsampled CD track were then processed through EXE Consulting's Engulf Audio(tm) software to produce a high-quality stereo image. This high-quality stereo image simulates a binaural recording, including stereo separation, echo, and reverb, all calculated in a self-consistent manner by solving the 3-D wave equation for a point source in a large enclosure. The simulated environment was a large concert hall. The absorption (reverb time T60) was set to 0.30 seconds for 100 Hz and 0.20 seconds for 4,000 Hz. These reverb times are very short for a large concert hall, but the tape is conversation, so the absorption was increased (T60 decreased). As is well known, reverb times should be shorter for speech than for orchestral music in order to maintain speech comprehension. The ideal listening environment for this simulated binaural recording is studio- quality headphones, but with the fast absorption (short reverb times), the use of computer speakers in an acoustically dead office space was found to be acceptable. We used primarily studio-quality headphones for our testing. Normally, this type of step would be performed later rather than earlier. The reason for performing this step first was to create a stereo image so that following processing steps could be more readily monitored using studio-quality headphones.

Both stereo images were subjected to dynamics processing (compression and expansion) to bring up low-level sounds, then noise-reduced using Syntrillium's CoolEdit 2000. Noiseprints were taken from the stereo images themselves during relatively quiet sections. The tape, in particular, produced a very noise-free 24/96 stereo WAV file. The CD track was very noisy to begin with, so didn't produce as noise-free a WAV file.

Both 24/96 stereo WAV files were then downsampled to CD-quality (16- bit, 44,100 stereo) images, then compressed using the Fraunhofer Institute's MP3 algorithms, licensed by Syntrillium for their CoolEdit 2000 program. The images were compressed at a rate of 256 KBits per second. They are joint stereo, MPEG-1, layer 3. (See Reference <2> for a summary of MP3).

General Characteristics of Recordings

The cassette recording begins with Patsy Ramsey saying, "?55 Fifteenth Street." The "7" digit is cut off at the beginning, but something sounding like the ending "n" sound can be heard. It is possible that whoever made the cassette tape copy neglected to take into account the unmagnetized tape leader at the beginning of the cassette tape.

The cassette recording ends with what appears to be typing by the 911 dispatcher. There is a final louder click sound as if the dispatcher hit a particular key harder than the others. The CD track begins with buzzing, a quick series of pops, a couple of separated pops, more buzzing, a very brief amount of noise, then a click which probably was the connection to the Ramsey phone line being made. Patsy Ramsey utters something immediately after the click, then the dispatcher says, "911 Emergency." Patsy then utters something else which cannot easily be distinguished, then says, "Police!" The 911 dispatcher starts saying, "What's going..." Then Patsy says, "?55 Fifteenth Street," the point where the cassette recording starts. It is difficult to hear the "7" of the Ramsey home address in this case because the 911 dispatcher is talking at that point, as Patsy interrupts her.

The CD track appears to contain another audio section beyond the point where the cassette tape recording ends. Immediately after the point where the cassette recording ends at what sounds like a final, loud key click, there is a three or four second section of a buzzing sound on the CD track, the same as that at the beginning of the track. Then there is a very brief section of noise like an open microphone followed by a pop. Following this is a section of noise similar to that which can be heard earlier in the track, immediately after the 911 dispatcher said, "Patsy?" for the last time and prior to her typing sounds. This later noise section is three or four seconds long. A short series of pops occurs, then a short section of buzzing sound on top of the noise ends the CD track.

The bulk of the recordings are very similar, as would be expected. A very notable difference between the recordings is that popping noises occur throughout the CD track that cannot be heard on the cassette tape recording. The CD track is in general much noisier than the cassette recording. It appears to be a poor-quality digitized version of what is contained on the cassette tape plus additional preceding and succeeding audio; however, it does contain this additional, critically important information, from a forensic standpoint, at the beginning and end of the track. These additional audio sections were used to draw conclusions about the controversial audio sections which some claim contain conversation. It is important to note that the controversial sections are NOT contained in the additional audio sections that are only on the CD track; the controversial sections potentially containing barely perceptible conversation are on BOTH the cassette recording and the CD track.

Purported Conversation

The audio section of both the tape and the CD track that contains purported conversation begins shortly after the 911 dispatcher says, "Patsy?" for the fourth time with noise that could possibly be interpreted as "We're not speaking to you" and ends with a very brief bit of noise resembling "What did you find?" and containing what sounds like a final, hard keystroke. A separate MP3 file was created for this particular section from the audio cassette. This should help listeners locate the controversial section without having to search for it. This section has slightly different audio processing performed on it in order to help bring out the purported conversation so that listeners can easily identify the "We're not speaking to you" and "What DID you find" sections. Please refer to the Appendix for more complete details on audio processing of this section.

Analysis of Noise

Several loops were created from short audio sections extracted from both the digitized cassette tape and the ripped CD track. Audio sections were extracted from the purported conversation between the Ramseys after the 911 call was assumed to be completed, from a section prior to the 911 call being connected to Patsy Ramsey, and from another section on the CD track which appears not to be the call from Patsy, but is perhaps part of the recording of a subsequent call.

Immediately prior to the connection being made to Patsy Ramsey, there is a very brief audio section (hereinafter #1) on the CD track that contains noise that sounds as though it could possibly be conversation. After the last time the 911 dispatcher says, "Patsy?" (the fourth time), there is another audio section (#2) which is relatively quiet except for some noise which sounds as though it could also possibly be conversation. It has been alleged at various times since December 1996 that this conversation was John Ramsey saying something like, "We're not speaking to you." This audio section is contained on both the cassette tape and the CD track. At the time near the last audible (what is assumed to be) key press by the 911 dispatcher, there is another section (#3) with noise which could possibly be conversation. This has been alleged to be Burke Ramsey saying something like, "What DID you find?" This section is contained on both the cassette tape and the CD track. A final audio section (#4) containing similar noise to section #2 is contained only on the CD track and follows a section of buzzing which resembles that of an amplified ground loop where the ground loop is close to electrical equipment such as a computer. Section #4 also sounds like #1 which is immediately prior to the connection being made to the Ramsey phone line.

This last audio section lasts about seven seconds and is somewhat of a mystery. It is not contained on the cassette tape at all, and it appears to have nothing whatsoever to do with the call from Patsy. The intervening buzzing sound between the audio sections #3 and #4 is very similar to the buzzing sound at the very beginning of the CD track, before audio section #1 starts. During both of these buzzing sounds, there is no audible input whatsoever, that is no discernible background noise such as from an open microphone or anything else such as that. This intervening buzzing sound is the strongest evidence that audio section #4 has nothing to do with Patsy's call. It is fortuitous, however, that it appears to have the same type of noise as does the recording of Patsy's call, as if it were from the same original recording system, perhaps something like a hangup call that came in soon after Patsy's call.

The extracted audio sections were processed again, separately from the rest of the recordings, in order to determine whether or not they contained conversation. It was noted early on that these noises had higher frequencies than should be passed over the Ramsey phone line; they were also very mechanical sounding in their cadence and precision and in their apparently repetitive nature.

Certain of these audio sections were overlaid with each other, one in the stereo Left channel, the other in the stereo Right channel. With this arrangement, the timing of the audio sections could be independently altered until a common sound was heard from both the Left and Right channels. If some sort of repetitive machine noise was present, it should be possible to synchronize the sounds from the two channels so that they became one, at least for any common, repetitive source. We found that we could do this with, for example, section #2 in the Right channel and each of the others in the Left channel. The composite sections were then looped a number of times for ease of listening. It is much easier to comprehend a short audio section if it is repeated a number of times.

The cassette recording was judged to be probably the most faithful rendition of the master recording (evidence tape), even though we did not have access to this master. We judge this because of the excessive amount of extra noise on the CD track. With respect to the digitized audio cassette recording , it was possible to overlay only audio sections #2 and #3 because sections #1 and #4 were not present on the audio tape. Nevertheless, it was possible to find a particular offset time, the same as for the CD track, which seemed to join these sections together. Some of the noise was very similar in both channels. In particular, the cadence of the two was suspiciously similar.

Two additional loops were made from this overlay of #2 and #3 ("We're not..." and "What DID...") from the digitized audio cassette recording, one with low-pass filtering, the other with high-pass filtering. The filtering had a strong effect on certain portions of the noise and not on others, depending on which type of filtering was performed. If the noise had been conversation from a single individual uttering a sentence, one would not expect a strong filtering effect which caused the first part of the sentence to disappear almost completely yet leave the latter portion almost intact. One would also not expect two completely different utterances (one a statement and one a question, no less) by two different individuals to have the same cadence. Nor would one expect that word of sentences uttered in ordinary conversation to be precisely timed as though they were mechanically produced.

To summarize, the loops created were:

CD track

1) Overlay of #2 ("We're not...") in Right channel to #1 (prior to connection) in Left channel.
2) Overlay of #2 in Right to #3 ("What DID...") in Left.
3) Overlay of #2 in Right to #4 (end) in Left.


1) Overlay of #2 in Right to #3 in Left with high-pass filtering.
2) Overlay of #2 in Right to #3 in Left with low-pass filtering.

Please refer to the Appendix for more complete details.


CD track:

Overlay of #2("We're not...) to #1 (prior to connection):

The noise loops from the CD track demonstrate a repetitive noise which is present at various times throughout the track. In particular, some of that repetitive noise was detected before the 911 dispatcher answered the 911 call from Patsy Ramsey, audio section #1. A portion of this noise is indistinguishable that of #2. The previously purported conversation by John Ramsey, said to be something like, "We're not speaking to you" could very well be this repetitive noise ("We're not speaking...") plus a second, narrow-band "hooting" type of noise ("...to you") that appears to be centered at approximately 500 Hz, as determined from the tape overlay. The narrow-band hooting type of sound is repeated during the sounds that are probably the 911 dispatcher's typing. The repetitive noise ("We're not speaking...") may simply be drowned out at this time by the typing sounds. It is a part of this "We're not speaking..." section that is similar to the noise of audio section #1, recorded prior to the 911 dispatcher answering the call from Patsy.

Overlay of #2 to #3 ("What DID..."):

The overlay of sections #2 and #3 displays a very similar cadence for the two different sections. This should be very surprising if one is expecting John Ramsey to be saying, "We're not speaking to you" and Burke to be saying "What did you find?" These sections are too mechanical and precise to be ordinary human conversation. In addition, as just previously mentioned, the long 'u' sound of "...to you" does not have the same spectral characteristics as the part "(We're) not speaking..." because the high-pass filtering does away with the former but not the latter, as determined by the tape overlay below.

Overlay of #2 and #4 (end of track):

The overlay of sections #2 and #4 reveal a repetitive background noise that sounds somewhat like a dishwasher operating can be heard in both channels at the same cadence. The cadence is precise enough that it would appear to be a machine noise rather than speech, unless someone is purposefully speaking in a very mechanical and unnatural manner.

Summary of CD track overlays:

Our conclusion is that there is no discernible conversation during the purported "We're not speaking to you" and "What DID you find?" sections of the CD track, but that these are instead composed of background noises, possibly modulated by the recording equipment, for example the automatic gain control (AGC) which is particularly evident after loud keystrokes. In particular, the section that precedes the 911 dispatcher's answering of the 911 call (#1) cannot possibly contain speech by the Ramseys, yet this early background noise is indistinguishable from the noise that is part of purported conversation between the Ramseys (#2). One can easily fool oneself into believing that there is conversation, but a more careful examination of the recording, complete with comparisons of one section of the recording to another by superposing them together in separate stereo channels, allows one to hear that the background noise is repeated at various times throughout the recording. Other noises are recorded on top of this repetitive background noise, especially the long 'u' sound, and this causes the noise to appear not to be as repetitive as more complete analysis shows it to be. There is also some sort of automatic gain control in operation, as was previously mentioned, which may very well be causing the repetitive background noise to appear to come and go.

Tape Overlay:

When listening to the overlay of samples extracted from the digitized audio cassette recording which are high-pass filtered (6,500 and 16,000 Hz bandpass), one can hear ample signal of purported conversation which, in that case, sounds like clicking that is distinct from the clearly audible keyboard typing sounds. But this shouldn't be the case because phone lines have a fairly steep cutoff at about 3,000 Hz. Moreover, the long 'u' or "hoot" sound is practically gone. With low-pass filtering (375 and 750 Hz bandpass), we hear hooting sounds and something from the "What DID you find" purported conversation, but not much of the other purported conversation. Conclusion: As with the CD track overlay, these noises have different spectral characteristics from voice, and the hooting type of noise is again found to have different spectral characteristics from the clicking type of sound.

Summary of all overlays:

There appear to be at least four different noise sounds: the background repetitive noise, the purported "What DID you find," the purported "We're not speaking...,"and the "...to you" hooting type of sound. None of these have the spectral characteristics of voice over a phone line, although perhaps the "...not speaking..." comes closest in our analysis. These noises all have different spectral characteristics from each other. If someone said, "(We're) not speaking...," that same person did not say, "...to you." Also, because the hooting ("...to you") sound is repeated at intervals during the typing, and because it is fairly narrow-band, it is unlikely to be the voice of anyone. A very short instance of this sound is also heard after the click of Patsy's hangup, immediately before the third "Patsy?" The purported "What DID you find" noise is too broad band to be voice over a phone line. The "(We're) not speaking..." noise has too many high frequencies at certain specific times (clicks) to be voice over a phone line. There appears to be some sort of underlying mechanical cadence to some portion of all the audio sections, even though all the sections do display different spectral characteristics. Also of interest is that the purported audio sections and the occurrence of the hooting sounds during the typing occur in an almost periodic fashion <3>.


After extensive processing and analysis, we conclude that recordings of the 911 emergency call made by Patsy Ramsey to report the kidnapping of her daughter JonBenét do not contain any audible conversation between any of the Ramseys following Patsy's hanging up the phone. There are too many discrepancies between the expectations of voice characteristics and the characteristics of the noises which some have reported as conversation for the hypothesis of additional conversation on the recording to be accepted. There appear instead to be several different noises with different characteristics, including at least one that has a cadence and is repeated. It is suggested that the combinations of these noises provide merely an appearance of conversation, particularly to wishful thinkers after the idea of conversation has been suggested to them. Unfortunately this noise has not only been falsely portrayed as conversation, but the idea that it is conversation has been bootstrapped into a demonstration of deception by the Ramseys, and then to a virtual proof of the guilt of at least one of the parents.

Further work could be done to test the actual evidence tape to verify these findings, although one shouldn't expect that the spectral characteristics would be appreciably different; however, one may find that certain noises that are on the audio cassette and especially on the CD track not to be present on the evidence tape. One or more of the several noise sources we found may be due to copying rather than due to the original recording. Unless one of these potential copying artifacts is masking something, we expect the same conclusions would be reached regarding the lack of audible conversation from the Ramseys' phone line after Patsy hung up the phone. We also don't expect any revolutionary findings because after various enhancements, we do clearly hear something that we could imagine, with a little effort, to be "We're not speaking to you" and "What DID you find?" It would also perhaps be beneficial to produce a better-quality audio CD for distribution by the District Attorney's office. It may also prove beneficial to determine the actual audio environment during the recording of Patsy's 911 call, although it may be far too late to do that accurately if the environment has changed considerably.

Thanks to the Boulder County District Attorney's office for providing the audio cassette and audio CD. Thanks to "Jameson" of www.webbsleuths.com for encouragement in this project.

References and Notes

<1> An attempt was made to acknowledge trademarks the first time they are encountered in this document. CoolEdit is a registered trademark of Syntrillium Software Corporation. WaveLab is a trademark and Steinberg is a registered trademark of Steinberg Media Technologies AG. Engulf Audio is a trademark of EXE Consulting. Pioneer is a registered trademark of Pioneer Electronics (USA) Inc. Behringer is a registered trademark of Behringer International GmbH. Nero is a registered trademark of Ahead Software. MP3 is a registered trademark of Thomson Multimedia. Maxell is a registered trademark of Hitachi Maxell, Ltd. Creative Labs is a registered trademark of Creative Technology Ltd. Plextor is a registered trademark of Plextor Corp. Pentium III is a registered trademark of Intel Corporation. Microsoft and Windows are registered trademarks of Microsoft Corporation. Other trademarks are trademarks of their respective holders (obviously).

<2> The following web page contains a good summary of what MP3 is all about as well as links to related pages:


<3> The mechanically repetitive noises during this section sound something like "...to you," "HOOT-hoot," "HOOT-hoot," "What did..." on the tape and "...to YOU," "hoot-hoo-hoo-HOOT," "hoot-hoo-hoo-HOOT," "What did you find" on the CD track. Closer examination indicates that the "hooting" sounds are also composed of more than one sound. One is almost a short, squawking or squeaking sort of hoot whereas the other one, usually following the former by a half second or so, is quieter and more drawn out. The short one is particularly noticeable in two occurrences during the typing that follows the purported "We're not speaking to you."


Specific processing steps.

A) Cassette tape digitizing and processing steps were as follows to produce MP3 file:

Recorded with Steinberg WaveLab Lite: 24-bit, 96,000, monophonic into
a Microsoft® Windows® RIFF format PCM WAV file:
Pioneer CW-650R dual-cassette tape deck to
Behringer EurorackMX802A mixer to
Terratech EWX-2496 master recording sound card.

Engulf Audio from EXE Consulting to create high-quality stereo image:
Concert Hall room (22.51m X 37.51m X 15.01m)
Binaural simulation: Solutions obtained at (11.135m, 15.0m, 3.0m)
(Left) and (11.375m, 15.0m, 3.0m) (Right) in left-handed
coordinate system. Point source placed at (11.135m, 6.0m, 3.0m)
in same system, 9.0m from Left solution. Solves 3-D wave
equation, providing stereo separation, echo, and reverberation in
a self-consistent manner.
Absorption: T60 = 0.30 seconds at 100 Hz, 0.20 seconds at 4000 Hz.
Reverb times kept low to maintain speech comprehension.
Designed for headphone listening.
The reason for performing this step first was to create a stereo
image so that following processing steps could be more readily
monitored using studio-quality headphones.
During this process, the resulting file is normalized to very nearly
0 db while the data are being maintained as double-precision
floating point.

CoolEdit 2000 from Syntrillium for the following steps:
Dynamics Processing:
flat 1.00 : 1 above -20 dB
cmp 2.00 : 1 below -20 dB
exp 10.5 : 1 below -96 dB
Noise Reduction (primarily removed noise produced by tape deck):
Noiseprint from section at end of digitized recording of
cassette tape
4096-point FFT
40 db reduction
Smoothing Amount = 2
Flat, 100%
Trimmed end and beginning to remove non-cassette tape audio
sections. These sections are NOT part of the cassette tape but
were produced between the time the digitizing program was started
and the tape deck was started AND between the time that the tape
deck was stopped and the digitizing program was stopped.
Downsampled from 24-bit, 96,000 samples per second stereo to CD
quality (16-bit, 44,100 samples per second stereo),
Compressed as MP3 using algorithms licensed from Fraunhofer
Institute. 256KBits per second, constant bit rate, 22,050 Hz
maximum band width, "High Quality" Codec.

B) The CD track was ripped from the audio CD using Ahead Nero into a
CD-quality, Microsoft Windows RIFF format PCM WAV file (16-bit,
44,100 samples per second, monophonic). Then the following steps
were performed:

Conversion of two-channel identical monophonic to single-channel
monophonic by removing right channel data using Syntrillium's
CoolEdit 2000.

Engulf Audio from EXE Consulting, same conditions as for the tape
(above, part A).

CoolEdit 2000 from Syntrillium for the following steps:
Dynamics Processing, same settings as for tape (above, part A).
Noise Reduction:
Noiseprint taken from approximately time = 8.95 seconds to 9.85
4096-point FFT
40 db reduction
NR Level 53
Sloped Noise Reduction Level: 0 Hz -30.2 %, 48,000 Hz -100%
Precision Factor = 5
Smoothing Amount = 2
No trimming was performed.
Noise samples for part C were extracted into separate files.
Downsampled from 24-bit, 96,000 samples per second stereo to CD
quality (16-bit, 44,100 samples per second stereo),
Compressed as MP3 using algorithms licensed from Fraunhofer
Institute. 256KBits per second, constant bit rate, 22,050 Hz
maximum band width, "High Quality" Codec.

C) Four noise samples were taken from the 24-bit, 96,000 samples per
second, stereo file that was upsampled from the CD track (see part
B above) and were each further compressed according to the
flat 1.00 : 1 above -10 dB
cmp 2.99 : 1 below -10 dB
exp 15.3 : 1 below -96 dB

The samples were:

1) From position at beginning of CD track, time = 8.95 seconds to 9.85

2) From time = 1:18.67 to time = 1:20.10.

3) From time = 1:23.69 to time = 1:24.67.

4) From approximately time = 1:28.6 to approximately time = 1:32.9.

Noise samples #1, 3, and 4 were edited so that only the left channel

Noise sample #2 was edited so that only the right channel remained.

Each of noise samples 1, 3, and 4 were overlaid one at a time to noise
sample 2. Noise sample 2 remained in the right channel while each
of the others remained in the left.

Noise samples were then adjusted in overlay so that a repetitive
background noise common to both the left and right channels was
synchronized. Although there were other noises in the recordings,
the common noise, somewhat like that of a dishwasher in operation,
could be heard in both left and right stereo channels. The
offsets used were: -0.2 seconds for #2 overlaying #1; -0.4 seconds
for #2 overlaying #3; +0.7 seconds for #2 overlaying #4. The
offsets are defined as the offset of the zero for #2 relative to
the zero of the section to which it is being overlaid, with "zero"
being defined as the beginning times listed above for each audio

The FFT filter "Mackie Mid Boost" from Syntrillium's CoolEdit 2000 was
applied so that the repetitive noise common to both channels could
be heard more clearly.

After trimming, the three overlays were each looped eight times for
ease of listening, then they were concatenated into a single file
with a 0.3 second silence between them.

The resulting concatenated file was then downsampled to CD quality,
then compressed into an MP3 file with the same settings as used

D) Two noise samples were extracted from the digitized version of the
cassette tape. These two samples correspond to #2 and #3 above
(see part C above), the only corresponding ones that are available
on the cassette tape recording:

After Engulf Audio processing, samples were extracted.

Overlaid with 0.3 seconds offset --- times not same for cassette
recording as for CD track due to difficulty of locating zero.

Trimmed to area of overlap only.

Dynamics processing:
flat 1.00 : 1 above -10 dB
cmp 2.99 : 1 below -10 dB
exp 15.3 : 1 below -96 dB

Filter FFT Mackie Mid Boost

Quick Filter:
hi: 187, 375, 750, 1500, 3000, 48,000 Hz sections of filter: -30
db; 6,500 and 16,000 Hz + 3.7 db
lo: 187, 1500, 3000, 6500, 16,000, 48,000 Hz sections of filter: -
30 db; 375 and 750 Hz + 3.7 db

Amplified: +6.0 db boost.

Created loops, then MP3 files:
high: looped eight times, then normalized, downsampled to CD
quality, compressed to MP3 at 256 KBits per second.
low: downsampled, looped eight times, compressed to MP3 (not
normalized) at 256 KBits per second.

MP3's used "High Quality" codecs as before.

E) An MP3 file was created from the purported conversation on the
audio cassette recording. This section begins shortly after the
fourth time that the 911 dispatcher says, "Patsy?" It was
processed with the following:

Normalized to 0db

Dynamics processing (to bring up low-level sounds):
flat 1.00 : 1 above -10 dB
cmp 2.99 : 1 below -10 dB
exp 15.3 : 1 below -96 dB

FFT Filter, bandpass (lessen hum):
220 Hz, 0%; 656 Hz, 100%; 2350 Hz, 100%; 8106 Hz, 0%
2048-point, Blackman-Harris windowing

Dynamics processing (to bring volume of keystrokes down):
cmp 3.00 : 1 above -30 dB
flat 1.00 : 1 below -30 dB

Amplify 400%

Engulf Audio from EXE Consulting, same conditions as for the tape
(above, part A).

© Copyright "Dave" on Jameson's Webbsleuths 2003. All rights reserved.

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