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One basic distinction in acoustics is the one between sounds that oscillate with a pattern that is repeated over time and sounds that are chaotic in nature, and show no repetitive pattern. Sounds of the first type may be referred to as "tones". There are a few tones that can be described by a very simple mathematical equation, for example the the square ...


28

What's lacking is mostly raw number-crunching ability. The MP3 format is relatively lightweight, and can be implemented using only fixed-point math (no FPU required), but it still takes a fair amount of computation to turn compressed frequency-domain data into uncompressed time-domain data that can be fed to a DAC. This IEEE article quotes a minimum ...


24

No hardware revisions are necessary. The digitization playback is achieved by bit-banging the volume register of the SID chip to simulate a digital playback device. Essentially, the SID can be used as a 4-bit digital playback device. What's amazing is that the thing sounds as good as it does playing back digital data. A great article about digis on the ...


22

Many PSG's (Programmable Sound Generators) at the time (such as the popular AY-3-8910) were made for applications like doorbells, kiosk machines, etc. And, of course, arcade machines and computers. The reason they had noise channels was simple. We need a way to synthesize sounds like drums, snares, and explosions. The best way to do that is to use random ...


20

I know of two ways of achieving polyphony in system with 1-bit audio systems: The simple way: time-multiplex two or more frequencies. For example, if you want the system to produce a mix of two tones, which are pure square waves in origin like these: you can simply render a period of first tone, followed by a period of second tone, and again, a period of ...


12

And these systems had not just a single audio channel, but a single-bit audio channel. There are no doubt many techniques, but a simple approach is to rapidly interleave the output of two or more channels. The low-pass filtering of the speaker will serve to effectively mix the channels together. Not the greatest fidelity but better than nothing. As an ...


12

Mp3 is primarily a lossy compression format for audio. It must be decompressed, and the process needs a lot of CPU time (as for retro computers.) Modern computers both have speeds good two orders of magnitude higher, and CPUs with specialized "multimedia" instructions that streamline operations like fast cosine transform. A trivial operation like "flip a ...


11

In some systems, the noise channel could be used as a cheap source of pseudo-randomness, such as in the Atari POKEY (read address 0A). Here, cheap means that the CPU can do other things whilst the randomness is being generated. This is useful because decent randomness is expensive to compute on general purpose hardware. Taking the example of the Atari POKEY,...


11

Just wanted to add a historical note (as this is retro computing). All Manchester computers from the earliest days generated sound by attaching a speaker to a single bit of a register (usually the accumulator). This sound was used to monitor the activity in the machine; because it if crashed or halted unexpectedly the sound would cease and if it was stuck ...


7

The best audio quality was obtained with pulse width modulation using the square wave voice. The oscillator was set to 0 and the pulse width was set by flipping the pulse width from 0 to maximum. With the CPU speed at 1mHz the fastest pulse switch rate achievable is around 15kHz, producing a sound wave of 7.5 kHz or less. Setting the low pass filter help ...


7

Any cassette tape system which can utilize a standard cassette tape recorder can be plugged into any audio device, with sufficient quality, and will work. You can record saved files with any audio recording app and load it back in by playing it back. I know this is regularly done on the Apple II, Sinclair ZX Spectrum, and Tandy Color Computer systems, and ...


5

There are many acoustic events - drum beats, steps, explosions, breath, abrasion, clicking... that are based on a lot of harmonically unrelated frequencies in relatively irregular patterns. Which is more easily synthesized by taking noise and filtering/ADSR-ing the unwanted parts away than controlling a lot of oscillators independently. Note that true white ...


4

There were also some more recent creative alternatives taking advantage of filters and undocumented test bits as well. Check out the Cubase64 demo by Mahoney: http://www.livet.se/mahoney/cubase64 You can also find versions of it playing on the real thing on YouTube, naturally. (spoiler alert: your face will melt -- it's that awesome.)


4

In the Spectrum lexicon, a t-state is just a "time state" — a single cycle of the ~3.5Mhz clock. For implied evidence of that, see e.g. this document of 128K ZX Spectrum Technical Information, which states ... there are 70908 T states per frame, and the '50 Hz' interrupt occurs at 50.01 Hz. 70908 t-states per frame * 50.01 Hz = 3.546 million t-states ...


4

Like others already answered: old CPUs does not have enough MIPS, and/or they are lacking instructions that would helped in MP3 decoding algorithm (remember that MP3 is standardized in 1995.). Nice example of 1992. computer that can play MP3 out-of-box is e.g. Atari Falcon030 from 1992. Despite slow main CPU, MC 68030 at 16MHz, Atari Falcon also have ...


4

Early 68k processors implemented a multi-cycle multiply instruction (70 cycles per MULx), so the inverse MDCT would likely be the limiting factor in terms of raw CPU time.


1

Many games have explosions. Explosions seem more like explosions when there's an associated a burst of noise than when there's a beep. Having other kinds of noise for things like engines is also good, but it's not too hard to get decent rumbly sounds out of tone generators. Explosion noises, however, would require changing the frequency setting much more ...


1

I have tried to save or load from a smartphone and PC. These don't record well. However the audio file from tape may be processed on PC. Audiotap and CS1er are examples of software for the TI. I have tried successfully to use an MP3 player (including through Bluetooth) to play wav files. A repossitory for wav files is at whtech: https://computerarchive.org/...


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