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By ryurkovich
#198800
Hello,

I'm looking for some help with an odd project I'm working on for a Natural History Museum.
We are in the process of creating an "Animal Sound Piano" with 12 MP3 Trigger boards, each has 18 triggers hooked up to a receiver.
There are 18 different animal inserts that activate its corresponding trigger when a key is pressed.
The sound of that animal then plays through a small speaker. (I have pictures but I couldn't figure out how to attach them to this.)

My questions are:
1. Is there a way to adjust the overall volume on the amps?
We have a couple lower frequency noises that are quieter even when clipping (ex bullfrog).

2. I've managed to get the mp3 files to play without a delay, by converting .wav to .mp3 through VLC.
The audio files were edited and exported through Adobe Audition. But I found that when I exported them straight from audition to .mp3 there was a delay when triggered on the MP3 Trigger. Do you know why this may be/ is there an easier way to do this?

Thanks for your help,
Rachel
User avatar
By robertsonics
#198810
Don't know how to answer the volume question since you haven't told us anything about the amps. This doesn't appear to be a question about the MP3 trigger, or is it? Not sure I understand.

The most likely reason for a delay when triggering a sound is that there is non-audio data at the beginning of the file. When you save the file from Audition, you need to make sure you tell it not to include any meta-data or tags.
By Yvan
#198828
Dear colleage,

I say colleage because I also work in a Natural History Museum.

You can use the .ini file to set all the boards the same output volume. Example and explanations are provided on https://robertsonics.com/mp3-trigger-downloads/

#VOLM 0 - sets the output volume of ther board to maximum.

If you create the same .ini file on each board, the output shall be the same on all your boards.
If you use a small speaker on each board (12 speakers in this case), they shall all play at the same volume.
Remember that sounds are the most difficult things to manage in a museum or science centre.

Concerning the delay, try to open the sound file with Audacity (it's free and very powerfull tool). Don't forget to download ant install the add-on LAME for Audacity.
Open your file and then export it as .mp3. There shouldn't be any "blank" time at the beginning.

I hope that this will help you.
Best regards,
Yvan.
By ryurkovich
#198855
Thank you both for your recommendations.
It is likely that I did export the files with meta-data causing the delay.

Yvan, I didn't have any .ini file on the cards for the boards, and tried one with the #VOLM 0 - the volume didn't seem different, so it must default to the maximum volume without the .ini.

The amps I am using are the https://www.sparkfun.com/products/11044
The speakers I am using are the https://www.sparkfun.com/products/9151
User avatar
By DanV
#198857
Your speaker (0.5 W) will be overpowered by the amp (1.4 W).
Your amp runs at 100% power unless you add a volume control - which can only lower the output power.
Your amp is mono - not sure the loss of one channel will be very good.
If you're using the speaker without an enclosure, the sound quality will be poor.
You can boost the power of the amp (see the datasheet and comments on the amp page).
Parts express has many speaker modules that will handle the power and will enclose the speakers for good sound.
By Yvan
#198859
Dear colleague,

If I unserstand correctly, you have 12 boards (with 18 sounds on each) with 12 amplifiers and two or three problems.
1. delay at ther beginning of each sound
2. output levels are not the same.
3. problems with sound quality.

Without .ini file, sounds are played at maximum level.

As I told, Audacity should remove the heading meta-data or non audio data. It should also allow you to adjust (modify) the level of each audio track you process. But it's a long work: 216 tracks to process is much.
Also, don't forget to add a 10K ohms potentiometer on each amplifier. This can help. Refer to the link below.

*** Snippet out the Quick Start Guide *** look at https://www.sparkfun.com/tutorials/392#tips
If your audio source and amplifier have different AC power supplies (such as audio coming from a desktop computer), you may hear a loud hum in the output. To fix this, connect a jumper wire between the - side of the audio input and the power supply ground (PWR - header).

Because the amplifier outputs a 250Khz PWM-like signal, it could potentially radiate interference to nearby sensitive circuitry. For this reason, keep the wires between the amplifier and speaker as short as possible.
*** end of snippet ***

I hope that this helps you.
Keep me and the forum informed.
Regards,
Yvan.
By ryurkovich
#198869
For the speakers:
Are you saying that it'd be better if I got speakers that would be closer to 1.4 W?
Can you give me an example of a speaker enclosure that would help amplify this speaker?

If I were to look into getting another kind of 2" speakers, what requirements should I look for in terms of Ohms and Wattage to work with this amplifier? For example would something like this work? Power Handling (RMS)3 Watts; Power Handling (max)6 Watts; 8 ohm impedance.
https://www.parts-express.com/dayton-a ... uctDetails

__

Yes, the output levels are not the same, even though they are when playing the files off my computer - maybe the speakers just cant handle that frequency?

Thanks for the Audacity suggestion, I'll look into it. Its actually only 18 audio files, I've put the same ones on each card.
What would a 10K Ohms potentiometer do?

Thanks
User avatar
By DanV
#198870
If you drive a 0.5 watt speaker with 30 watts, it will damage the speaker in one or more ways.
We're only talking 1.4 watts but it is still over powering the speaker.
Any box you can put the speaker in will greatly improve the sound - even if you affix it to a deodorant can lid.
If you allow the sound coming off the back of the speaker to mingle with the sound from the front of the speaker in any way, it will cancel much of the sound output. And lower frequency response will suffer greatly.

I can't really tell what the overall frequency response of that particular speaker is but it would not require an enclosure since its back is enclosed.
This speaker is also very nice and the response is 150 Hz - 14KHz and is its own enclosure:
https://www.parts-express.com/m12-j-ful ... --289-2160

We also need to know what voltage you are powering the amp with.
It's rated at 6 VDC max. At 4.2 - 6 VDC the speaker minimum resistance is 6.4 ohm (so 8 ohm is good - 4 is obviously not good).
At 2.5 - 4.2 VDC the speaker minimum resistance is 3.2 ohm (so 4 ohm is good - 8 will provide reduced output volume).
By Yvan
#198876
Dear Rachel,

As I have an MP3 Trigger, as well as a Wav Trigger and a Tsunami board, I tried several things yesterday evening. ( But I don't own the same amplifier as yours.)
I also looked at a couple of audio files. I opened them into Audacity and zoomed on the very beginning of the files. They have a small gap (blank sound) for 0.3 to 0.5 second. This gap can be deleted without damage to the audio track.
Would you attach a couple of your files to your next post? If attachments aren't possible, send a link to a location where I can download them from. I'll look at them and see what we can do.
Regards,
Yvan.
By Yvan
#198878
Dear Rachel, dear colleague,

Without potentiometer, the amplifier shall output the sounds at maximum level by default (if I remember the documentation).
The 10K Ohms potentiometer allows you to adjust the sound level. In a museum ,or science centre, sounds can be too loud or too low... Just try the final good level.
But try also to set the same level of all your files
look at https://manual.audacityteam.org/man/cha ... ation.html
You can get all your files at the same source volume level.

Regards,
Yvan.
By ryurkovich
#198923
I tested a M12-J Full-Range Speaker Module 1-1/2" x 4-1/8" x 1" speaker (Power Handling (RMS)7 Watts; Power Handling (max)14 Watts
Impedance 8 ohms) with one of the units and it sounded great!

My worry is, if I added 12 of these speakers to the 12 separate boards&amps that are all powered by the same source, would the speakers require more power than the amps can handle?

The power supply I'm using is AC INPUT:110/240V DC OUTPUT: 5V 10A

I think I'm all set with the files, though.
Thanks!
By Yvan
#198927
Dear Rachel,

Each MP3 Trigger needs 85mA when playing. Let's say 100mA. This makes 1.2A for 12 boards.
Let's assume that each amplifier needs 500mA at max volume. This makes 6.0A for the 12 amplifiers.
Total: 7.2A ( < 10A); you mustn't worry.

Regards,
Yvan.
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