How these pages
make sound.

Method

What is calculated, what is sampled, what we will not publish

Pitch

Notes use twelve-tone equal temperament. A4 is 440 Hz unless a control on the page says otherwise. Frequency is 440 × 2^{(MIDI − 69) / 12}. Scientific pitch names middle C as C4 (MIDI 60, 261.63 Hz). Cents on a frequency page are the distance from the nearest equal-tempered note, rounded to the nearest cent.

Wavelength uses 343 m/s, the approximate speed of sound in dry air at 20 °C. It is a room-scale illustration, not a lab measurement of your room.

Tones and noise

Sine, square and sawtooth tones are oscillators in the Web Audio API. Pink noise is a Kellet filter over white noise, looped every few seconds with a short crossfade. A limiter (threshold −3 dB, ratio 20:1, fast attack) sits in front of the output so a full-scale sweep cannot slam the speakers. You still control the level. Steady tones cause fatigue faster than music. Stop if your ears ring.

Piano

Piano buttons play .m4a samples for MIDI 60–84, files numbered 1 through 25. Outside that range the nearest sample is played back at a different rate, which changes formant as well as pitch. That is why note pages also offer a sine wave.

Compression comparisons

The compression trainer uses DynamicsCompressorNode. Each drill has a target setting and a foil. Makeup gain is set so the two versions sit at a similar loudness. The gain-reduction meter stays hidden until you answer. Knee is fixed at 4 dB. These are listening examples, not a model of a specific analog compressor.

EQ pages

Instrument pages are starting points: a frequency, a Q and a reason. They are not mix prescriptions. Playback uses a peaking filter at about +9 dB or −10 dB, or a band-pass solo, on a stem we actually have (drums, bass, guitars, piano, strings, an electronic beat, a full mix, or pink noise). Vocal pages use the full mix because we do not ship an isolated vocal stem, and they say so.

What gets a URL

A page is published only when it has its own playable control, its own numbers, a self-referencing canonical URL, breadcrumbs and links to its neighbors. Query strings on the tools are not separate pages. We did not publish one URL per integer hertz.

The first published reference batch is: instrument EQ pages, twelve intervals, all 88 piano notes, a curated frequency list, the tempos producers look up, and major/minor keys and scales plus four chord qualities per root. Held back until measurement says the batch is being indexed: every remaining BPM from 60 to 200, the other chord qualities, and the other scale modes.

How we will measure, 3–4 weeks after deploy

• Indexed percentage for each sitemap family, in Search Console page indexing.
• Impressions per URL, and whether those impressions come from more than one query.
• Median position. A family stuck past position 50 with almost no impressions does not get a bigger sibling.
• Pause expansion if a family is mostly "crawled, not indexed", or if impressions per URL stay near zero.

Submit the sitemap index once. Do not request indexing for hundreds of URLs by hand. That does not make thin pages good, and it is not how this site is meant to grow.

Links that actually move a new domain

These are outside this website and still undone until a person does them:

• Set the App Store marketing URL to https://studioears.app/.
• Link the StudioEars name on coding.berlin to https://studioears.app/.
• 301 the old studioearsapp.com hostname to https://studioears.app/.
• Offer the free trainers to ear-training roundups and to teachers, one relevant page each, not a blast of every URL.

App Store buttons on this site add a campaign token ct=web-… so installs from a page can be told apart. That token is not a substitute for the marketing URL.