Genres of music and perceived noise

There are dozens of genres of music. Some are quiet; some are loud. Some have wide dynamic range (DR) and some have very compressed DR. Generally, the louder and more compressed DR, the less you’ll perceive the noise. And vice versa.

For example: if you plan to record hard rock, grunge or modern disco music with very narrow DR (highly compressed DR), then you even won’t hear the noise of a type I tape, which is the noisiest tape of all.

But if you plan to record some classical, soundtrack or acoustic, then you’ll need a quieter tape and probably a good noise reduction system.

Now I invite you to another experiment: take a listen to these audio samples and get your own conclusions. Here you’ll find two different songs (loud and quiet) being recorded on standard type I (TDK D) and II (TDK SF) tapes, with no NR at all.

What this teaches you is:

• The soundtrack (and any ‘quiet’ song) is very sensitive to tape noise due to its high dynamic range and will clearly benefit from using quieter type II tapes; not to mention a good NR system.
• With loud (or highly compressed dynamic range) songs it really doesn’t matter what kind of tape you use, at least in terms of noise.

Given those conclusions, I can summarize them in this graph when you can see the ideal use for the three tape types depending on the music to be recorded:

*: Of course, this music style scale is not absolute. There are metal songs that have very wide DR and soundtrack with very narrow DR, but I think you get the idea…

Level of noise and types of tape

As I already explained, every tape has its own characteristics, and that includes the background hiss.

As a rule of thumb, type I tapes are the noisiest, with levels that are around -50 dB. Type II (chrome) are much quieter* and go down to -59dB (which is up to 1.5 times quieter than type I). Type III (FeCr) was a commercially failed experiment, but they have a noise of about …-60dB. The noise level on Type IV (metal) is around -56dB (which is half noisier than type I).

*: This is in part due to the difference in playback EQ. The 70µs EQ pushes the treble several dB down.

Here you can hear real hiss of several tapes of each type, going from I to IV, in both qualities: basic/entry-level and high-level. The real hiss is low and not easily hearable so I amplified it to more than 3X its original level (20dB). Here you can compare the real hiss, a song (as reference) and the hiss amplified 20dB. You should start by adjusting your listening volume with the reference music sound level to your preference, and then explore the sounds, so you can have a true perception of the whole thing.

Now here you can explore the real background hiss of each tape:

*: The background hiss has been amplified 20dB for convenience, as that way is more clearly hearable.

Noise and dynamic range

So, given the data above, you can state that metal tapes aren’t as quiet as type II, but they have much more output level, and in the end they have more or less the same DR, so the same perceived noise (with some advantages in the treble, though).

• What?
• Yes, it can sound a bit technical but that’s true.

The zero reference level in the VU scale is just a reference level for recording and playing. If a tape can hold louder levels than another tape, you can either:

1. Hear it louder (just for no reason other than the tape is louder, which is nonsense).
2. Lower the volume to your taste and to match other tapes (which has sense). And… guess what? When you lower the volume you’re actually lowering the noise too.

As you can see, a tape that can hold louder levels is in practice quieter than another tape that has the same background level but lower output.

So, in the end what counts is the difference between the louder recorded sound (with good quality and low distortion, of course) and the background hiss. And that’s actually the dynamic range of the tape.

This graph shows the limits of every type tape and their dynamic range:

As you can see, metal and ferric tapes can have very high output level, but the background noise is very different between them. Another big difference between them is the clarity in the treble, which is great on metals but not so good in ferric tapes.

That means the dynamic range is different in each type:

Chrome tapes have the lowest noise but not so high output level as the others. But, in the end, what counts is the DR, because when you listen to those tapes you always adjust the volume to get the same perceived level, thus varying the hiss.

Here’s one example: A TDK SA-X ‘86, which is well known for its high reputation over the years, has a background hiss of -58dB and a MOL of +2.2 dB. Within the same year, a TDK MA-X has a hiss of -53.5 dB but also a MOL of +5 dB. As you can see the chrome has much lower noise than the metal, but the latter has much higher output than the former.

*: Actually this was not a true chrome tape but a double-coated ferric-cobalt tape. But I leave all that for another article…

So, in the end, what counts is that with the SA-X, the hiss is 60.2 dB below the music (58 + 2.2), and with the MA-X the hiss is 58.5 dB under (53.5 + 5), so the SA-X wins. The saturation in the highs is another story, though…

A big thanks to Terence (aka Wilhelm at Tapeheads forums) who has given me a lot of help with this article and, of course, to Vincenzo who is always helping me with technical and grammatical corrections. Also I have to thank Techmoan for his help finding a good title.