V. THE BELL SOUND
On the Channel-I recording, a bell-like sound is heard for about a third of a second, approximately four seconds after the end of the "Hold-Everything" phrase. BRSW have analyzed this sound and suggested it might be from a carillon bell. But no such bell could be located in the region where the motorcycle with stuck-open mike could be expected.
Steve Barber heard a similar sound on Channel-II recording at about the time displacement. On his information, we did a spectral analysis of the two recordings in this region. The two spectra are shown in Figure 10. They are on same scale and are aligned in time on the left which can be recognized as the second heterodyne of Channel I and the last brief tone of Channel II, in the "Hold-Everything" phrase. The bell sound is from approximately 14.45 to 14.80 seconds on Channel I (Figure 10(a), which has same time origin as Figure 3(a)) and 7.70 to 8.05 seconds on Channel II (Figure 10(b), which has a time origin different from Figure 3(b)). The two bell sounds are almost aligned. If there is any time difference, it is difficult to estimate as it is difficult to ascertain the exact starting time of the bell sound on both recordings.
The spectra of the bell sound contain two prominent tones around 1150 Hz and 1600 Hz. To ascertain if the two recordings have the same bell sound, we did a 10-Hz resolution spectral analysis of the bell segment and totaled energy in each frequency bin (up to 2500 Hz) in this segment. This is plotted in Figure 11. The two prominent peaks are at 1150 Hz and 1610 Hz on Channel I and at 1150 Hz and 1620 Hz on Channel II. These peaks are very sharp indicating them to be harmonics (pure tones) with a fundamental frequency of 230 Hz. At 230 Hz, Channel II has a prominent peak, and Channel I has a peak which is not very large in absolute terms but stands out against the background. This is perhaps due to some filtering on Channel-I recording which has attenuated low frequency components. The two prominent tones are fifth and seventh harmonics and their frequencies match exactly (within the 10 Hz resolution).
An interesting feature of this spectral segment is that other than these tones, the two recordings seem to have nothing else in common. This indicates that there was no cross-talk between the two channels during this segment and that neither recording was added on the other one at a later time. In this period, Channel-I spectra contain two strong heterodynes less than a second before the bell sound, which are clearly absent in Channel-II spectra. Likewise, during the bell segment itself, Channel-II spectra has very strong signal in 500-800 Hz range, which does not appear on Channel-I spectra. All these rule out the possibility of cross-talk from either channel to the other during this segment, implying that the bell sound was picked up independently by both the channels.
If the bell sound is due to a "physical" bell, the sound must have been picked up acoustically by the two channels. On Channel II, the sound occurs in the middle of a dispatcher transmission ("10-4, Dallas 1, station 5 will be notified.") This implies that the "bell" must be within earshot of the dispatcher's office and must be heard there. This also implies (since a time difference of 50 ms means a path difference of 50 feet) that the motorcycle with the stuck-open mike was not too far from the dispatcher's office which is in the downtown area far from the Dealey Plaza where the shooting took place. This in itself would invalidate the theory that shots were recorded on Channel-I tape.
Capt. James Bowles of Dallas Police Department informed us that there was no such bell in the neighborhood of the dispatcher's office and that the office is fairly well soundproofed making it impossible for such a bell to be heard inside the office. Steve Barber who works with musical instruments insists that this is not a bell sound. Also the duration of the sound is too short (only 350 ms) to be due to a carillon bell. Furthermore, sound from a physical bell will have some sort of exponential decay while this sound exhibits a very abrupt beginning and end.
With the above discussion, we conclude that this sound is not from a physical bell but perhaps an electrical disturbance which was independently picked up by both the channels which have many common carriers and components. Nevertheless, the "bell" is strong corroboration of our timing analysis, as this is certainly a tie point between two channels which happened in real time.
If such electrical disturbances are picked up on these recordings, there must be other such examples. Indeed, Steve Barber heard another bell-like sound on the Channel-II recording a little after 12:46 during another dispatcher transmission, "We should know something before long."
This bell sound is broken in two segments, with voice in between, and sounds like ding-dong. Figure 12 is the spectra of the sound. In this spectral calculation, no correction was made for the warp introduced by the turntable playback. Therefore on this spectra, the time scale appears compressed and accordingly the frequency scale expanded. The two bell segments on this figure are approximately from 10.40 to 10.60 and 10.85 to 11.10 seconds. Because of the warp, actual time intervals are longer than indicated.
On these spectra we notice horizontal bars which appear to be the harmonics of some base frequency. To confirm this, we did another high resolution spectral analysis (10-Hz resolution) and totaled the energy in each frequency bin for the two segments separately. This is plotted in Figure 13. The two most prominent tones in the first segment (10.40 to 10.60 seconds) are at 870 and 1310 Hz, which appear to be second and third harmonics with a base frequency of 435 Hz. There is another prominent tone at 1150 Hz which is not harmonically related to the other two tones. For the second segment (10.85 to 11.10 seconds) the two most prominent tones are at 850 and 1280 Hz which appear to be the second and third harmonics with a base frequency of 425 Hz. There is another prominent tone at 1610 Hz which is not harmonically related to the other two tones.
This bell sound is not heard on the Channel-I recording at a corresponding time. One likely explanation is that the Channel-I recorder was in the stop mode at that time. Even in the record mode, this electrical disturbance may not have been picked up by the Channel-I recorder. The presence of this second bell sound interrupted by voice and at 12:46 points to its likely origin as an electrical disturbance rather than an actual bell.
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