Simulator: components

The band has an old but usable computer with Abel installed on it, donated by Ed Donnen and the Washington Ringing Society, and a set of four muffles that fit the light four (1234).  This summer the band voted to buy a sensor setup, which arrived from England a few weeks ago.  Now it’s time to get everything set up.  Thomas started on this in earnest this week.

The computer · The computer is an old Dell Inspiration laptop, disabled by Ed Donnen so that it won’t do anything but run ringing software and has no attractive pieces for anyone to steal.  It sat in the bell tower unnoticed for several years.  When I first started it up it failed to boot due to some internal power storage having run down.  Ed said:  either press F1 when it offers that choice and see if it works, or leave it plugged in for a few hours to charge everything back up.  That worked.  I’ve left it plugged in and on since, to make sure no further problems arise.

Something to set the computer on · Computers don’t thrive or survive on the floor or stuffed in a corner, plus to use the simulator someone has to give commands to it.  My wife and I had an IKEA kitchen cart and not enough space to move everything to Virginia, so we donated it to the tower as a computer stand.  It’s the right size for the space and has enough area for the computer, some speakers, and the odds and ends of the sensor wiring.

The sensor setup · It consists of these components:

  1. (8x)  A reflector for each bell wheel, to give the optical sensor something to sense.
  2. (8x)  An optical sensor for each bell.  The sensor has a bright LED whose light the reflector can bounce back to the sensor’s receiver.
  3. (8x)  A cable from each optical sensor to the next piece.
  4. The Multi-Bell Interface or MBI, a box with eight jacks for the cables from the optical sensor and one jack for the main cable down to the computer.  The MBI multiplexes the sensor outputs onto one signal line, and probably does various other useful electronic tasks we need know nothing about.
  5. The main cable from the MBI to the computer.  It carries the multiplexed sensor signals down, and also carries power up to run the MBI and sensors.
  6. The small power supply for the MBI and sensors.

Someone had ordered a one-bell setup some years ago and the parts were still lying about the tower.  We shipped those back to David Bagley, who makes the sensor setups, for a discount on the price of our setup.  Everything arrived at the tower in July, where it waited until I had time to install it.

Bell silencers or muffles · My original plan was to construct a frame for each bell that fits in its mouth and around its clapper, preventing the clapper from swinging and thus the bell from sounding.  But moving troubles got in the way, and I never had time to make them.  The backup plan is to use the four muffles Ed Donnen made for the tower some years back.  These are sections of motorcycle tire that fit over a clapper.  Each has two flaps cut in it to let the clapper through and hold the muffle in place on the clapper.  If the tower finds it needs to run the simulation with more than four ringers, perhaps Ed will make more muffles for them.

Simulator: why it’s useful

We’ve been planning for some time to set up the tower for simulated ringing.  This involves:

  • a computer running Abel to produce appropriate bell sounds;
  • a configuration for Abel telling it how many bells we have and which pitch each one sounds;
  • an optical sensor for each bell to detect its motion;
  • wiring and electronics to connect the sensors to the computer;  and
  • a table of time delays for each bell to accommodate its natural period of swinging.

When everything is set up properly, each time a bell swings, its optical sensor detects the motion and sends a signal to the computer and Abel.  Abel waits the appropriate time delay and then plays an appropriate recorded bell sound.

Why is this desirable?  First, because the Miami tower tries to accommodate its neighbors and limit the amount of ringing they hear.  The simulator setup lets the ringers silence or muffle the bells, so the neighbors don’t hear anything, yet hear the simulated sounds that their ringing would have produced.  Thus the band can practice more often and longer.

Second, because the simulator can fill in bells that there are not ringers for.  In the past the band has often suffered from low attendance, with not enough ringers present to do anything.  The simulator can be set up to fill in bells for which there are no ringers, and sound each of those bells when a skilled ringer would have sounded it.  Using it a few ringers can work on Rounds, or Plain Hunt on any number of bells, or Plain Bob or more complex methods.  The band’s members vary in ambition and skill, like any band, and the simulator allows ambitious ringers to learn methods that the tower can’t provide a band for.

And finally, because the simulated bells strike exactly where they should be striking, enabling ringers who want to improve their striking above the band’s level to work as if surrounded by a band of skilled ringers.  In that context, any bell that strikes out of place is much more obvious, and it’s always clear which ringer was in error since the simulated bells are never out of place.

Clappers checked/realigned

Thomas checked the alignment of the clappers of the 3 and 6 and realigned the 3’s clapper.  These had worked loose and been spotted on 2013Aug13Tu and quickly realigned and tightened by Bobbie and Thomas, but we hadn’t had a tape measure and were pretty sure at least the 3 was not aligned correctly.  Thomas brought a tape measure today (and donated it to the tower) and using it aligned the 3’s clapper properly and confirmed that the 6’s had been properly aligned last week.

Nuts working loose

Bobbie and Thomas made a routine check of the bells before practice and found two loose wheel nuts (#1 and #5) and, much more seriously, two loose staple bolts whose clappers could no longer be kept swinging true (#3 and #6).

Each staple bolt is secured by two nuts, the lower of which holds the staple bolt (and thus the clapper) in place and the upper of which acts as a lock nut keeping the lower from loosening.  In both cases the lower nut had frozen in place, especially on the 3, and we first had to work it loose in order to be able to tighten it.  This took about ten minutes of back-and-forth with the 25mm wrench for the 3.  They need to be loosened and spun off, with the staple bolt and clapper supported by the staple bolt stand Thomas built for sawing off the 5’s lower staple bolt nut that had frozen in place.  Once spun off, the threads of the bolt and nut need to be brushed and wiped clean, coated lightly with lithium grease, then worked easy by spinning the nut up and down until the grease is spread and any roughness or corrosion is worked out.  Then each clapper can be realigned and the nuts tightened up again.

Changing of the guard

I am delighted that other ringers are stepping forward to take over the functions I’ve been performing, so that when I move in about a month the band will continue to flourish and progress.

  • Jody is taking over this blog, and started posting with yesterday’s practice.
  • Bobbie has taken over managing the attendance dudle and wrangling attendance for each ringing session, ensuring we have enough ringers, someone to run the ringing, someone to watch over ringers’ safety, and someone to unlock and relock the tower.  (For some reason the Miami band has not and still is not electing officers, instead preferring to wing it week by week.)
  • Jim has taken over managing the mailing list.
  • Nancy and Carroll are prepared and enthusiastic to take over the steeplekeeping, though by chance neither of them is in Miami at present and won’t be for possibly several months.
  • Anne has acted as ringing master for at least one session, and did so well by all reports.  Several other ringers have expressed a willingness to do so as well.

It will be bittersweet to leave the Miami ringers, even though I look forward to the future, but at least I can feel the tower is in good hands.

Rope bosses remounted

Eoin and Thomas spent five hours pulling out the old anchors, redrilling the mounting holes, installing deeper anchors, and remounting the rope bosses with longer screws.  All are firmly mounted now and will not be falling down.

Eoin steadied the bottom of the ladder and handed things up;  Thomas climbed up and down, drilled the holes with the vacuum cleaner nozzle sucking up the dust, blew out the remaining dust with a squeeze bulb, and reinstalled the bosses.

The bosses were originally mounted in 3/16″ holes with lead strips as anchors and plated #6 steel screws.  At some point about half the lead strips had been replaced with plastic expanding anchors.  Some of the holes were crooked or out of round, unfortunately.  We remounted first the treble’s boss (2011Nov), which had fallen in 2008 and been down for three years, and later the remaining bosses (2012Apr), using new expanding plastic anchors for the bosses that weren’t holding and stainless screws for all.  We cleaned the bosses, some of which had fungus from the old days when the bells were left mouth up and filled with water that then dumped out and soaked everything the next time they were rung, and put soft plastic gaskets on the upper sides to absorb movement from the wood’s expansion.  This was presumably an improvement but bosses were still working loose and the 6’s boss fell, twice.

The second time the 6’s boss fell we redrilled its mounting holes to ¼” diameter, straight and perpendicular (two had been crooked) and deeper to fit the longer ¼” anchors, and remounted it with #10 1½” stainless screws.

Today we did the same for the remaining seven bells.

Sound level reduced substantially by curtains

On Friday Carroll and Thomas brought the ladder down from the intermediate chamber and rehung the curtains that were taken down when the new windows were installed in mid-May, in the hope that this might mitigate the excessive sound levels.

At the June 4 practice with all eight bells going, the level was measured at almost 88dB, above the widely accepted threshold of 85dB.  Decibels are a logarithmic scale, with a difference of 10dB defined as a factor of 10 between the two power levels;  the 3dB difference from 85 to 88dB represents a factor of almost exactly two, so that 88dB is twice the power of 85dB.

At today’s service ringing, with all eight going, the meter showed slightly more than 76dB, less than one-tenth the power at 88dB.  Lower would be better (the NIH recommends less than 75dB) but at least this is out of the range in which permanent hearing damage is inevitable over time.

The curtains make a substantial difference and we will leave them up until a permanent and more attractive solution can be arranged.

Hearing-damaging sound levels in ringing chamber

2013Jun04Tu’s practice was the first opportunity since the curtains came down last month to measure the sound pressure level in the ringing chamber with all eight bells going.  On 2013May21Tu with eight bells going several ringers noted that it was uncomfortably loud.  For this week’s Jun04Tu practice several of the ringers came equipped with ear protection in expectation of all eight going.

Tonight with eight bells going, Thomas’s sound pressure meter gave readings ranging from 86dB to almost 88dB.  85dB is a widely accepted threshold for hearing damage;  here is an authoritative discussion from the National Institutes for Health, the third paragraph of which states:

Long or repeated exposure to sounds at or above 85 decibels can cause hearing loss. The louder the sound, the shorter the time period before NIHL [noise induced hearing loss] can occur. Sounds of less than 75 decibels, even after long exposure, are unlikely to cause hearing loss.

The rule of thumb I’ve seen (as a musician and a physics major) is permanent damage after one hour at 85dB.  People who ignore this risk soon don’t notice that it’s too loud because their hearing has been damaged.  A typical scenario for NIHL is for an unknowledgeable person to tough it out, often commenting that “it’s not really that loud”, especially after a few hours accumulated exposure when their hearing has become less sensitive due to the permanent damage.

We must take measures to prevent damage to the ringers’ hearing.  I will bring my supply of foam earplugs to this Sunday’s service ringing, for which 10 ringers are expected.  I ordered a box of the 3M “Push-in” earplugs that the Pittsburgh tower gives out (they have 85+dB levels too) which should arrive next week.  The push-in earplugs are easier to manage and don’t require clean hands like the foam earplugs do.  They are reusable.

Jim is talking of putting up wallboard over the concrete, which probably will reduce the sound level only slightly.  The figures I’ve found show gypsum board over concrete reduces the sound level by less than half a decibel relative to just concrete.  Just putting up wallboard will make the ringing chamber look better but the sound level will still be above 85dB.  The tower should push for something that will eliminate the cumulative permanent hearing damage that the current sound levels will cause.