Chapter 10 Exercises

This chapter's exercises are unusually physical: you'll be clapping in bathrooms, sliding mirrors along walls, and crawling around your floor with a bass line playing. Good. The room is the one piece of equipment you can't learn from a screenshot. Work the parts roughly in order — Part A locks the vocabulary, Part B calibrates your ears on real rooms (the DAW Lab assumes you've done at least B1 and B2), and Part C turns the diagnostics into files and evidence. Run everything at your Chapter 8 marked reference level wherever playback is involved; a room test at a random volume is two experiments pretending to be one.

Difficulty legend: ⭐ = foundational (do these even on a busy week) · ⭐⭐ = applied (the chapter becomes real here) · ⭐⭐⭐ = synthesis (Part D — argue, design, defend). Time estimates are honest averages. Selected exercises (marked ★) have worked answers in the back of the book (Answers to Selected Exercises).

Part A: Conceptual Understanding

A1. The three lies, from memory. ⭐ ★ (10 min) Without looking back at the chapter, rebuild the three-lies table: for each of the three families of small-room problems, write what causes it physically, what it sounds like at your chair, the $0 test that finds it, and the first fix. Then check against the chapter and note which row you knew least well — that's the row your room is most likely getting away with.

A2. Why the EQ can't reach it. ⭐ (10 min) A friend hears about your treatment plans and says, "Why bother? Just EQ your monitors flat — there are plugins that do it automatically." Write a four-sentence reply that covers both halves of the truth: why EQ cannot remove comb filtering (where, physically, does the coloration happen relative to the plugin?), and why boosting a modal null wastes headroom while leaving the hole — plus the one honest concession (what can careful correction EQ do for modal peaks, and why is it a supplement to treatment rather than a substitute?).

A3. The soundproofing untangle. ⭐⭐ (15 min) A forum post reads: "Drummer in a second-floor apartment. Neighbor below is losing it. About to spend $400 on a 24-pack of acoustic foam wedges to soundproof the room — which brand?" Draft a three-paragraph reply in this chapter's spirit: paragraph one, the difference between treatment and isolation, and which problem they actually have; paragraph two, why the foam will not help the neighbor at all (name the three things that actually stop sound crossing a boundary, and what each costs); paragraph three, the realistic move list for their situation — behavioral, positional, and cheap-mechanical — ending with where the $400 would do real audible good instead.

A4. The null arithmetic. ⭐ ★ (10 min) Your listening chair sits in a 60 Hz null. You boost your monitors 6 dB at 60 Hz. Walk through what happens, step by step, at three locations: your chair, the corner behind you, and a spot four feet to your left. Then state the rule in one sentence: what are the only two things that genuinely address a null, and why is one of them free?

A5. Mode-stack prediction. ⭐⭐ (15 min) Two spare rooms are available for your studio, both with 8-foot ceilings: Room X is 12 × 12 feet; Room Y is 9 × 12 feet. Using f ≈ 565 ÷ L, compute the first two axial modes for every dimension of both rooms. Identify every frequency where two dimensions land on (or within a few hertz of) the same mode, explain what stacking does to that frequency's behavior, and pick your room. Then the twist: name one non-acoustic reason that might still justifiably overrule your acoustic pick, because real studios are compromises with doors.

A6. Thickness is the purchase. ⭐⭐ ★ (10 min) Explain, using the picture of air movement near a wall, why a 2-inch mineral-wool panel does honest work at 2 kHz, partial work at 300 Hz, and nearly nothing at 80 Hz. Then explain two ways to extend the same panel's reach downward without buying thicker material, and finish with the blow test: what it checks, and what failing it costs your panel acoustically.

A7. Two rooms, two doctrines. ⭐⭐ (10 min) Your room must serve as both mixing room and tracking room. In your own words: what does each job need from the room, why is "deader is safer" the vocal-tracking doctrine but not a universal law for instruments, and what's the mobility strategy that lets one room hold both jobs? Include the cardioid-pattern logic from Chapter 7 that decides where the heaviest absorption goes when a singer steps up to the mic.

Part B: 🎧 Listening Lab

Your listening journal from Chapter 4 stays open for all of these. The skill being built here is the chapter's promise: hearing rooms the way you learned to hear frequency bands — instantly, involuntarily, usefully.

B1. The clap-test tour: five rooms. ⭐ ★ (25 min) The chapter's closing promised this one, and it's the foundation for everything else in this part. Take your hands on a tour of five rooms in your home (borrow a hallway or stairwell from your building if your home runs small): your studio room, a bathroom, a closet (head inside it), a hallway or stairwell, and a kitchen or living room. In each room, give one sharp clap and listen to the answer, then log three judgments: (1) flutter — any metallic zing or sproingy ring? Note which parallel surfaces you're standing between. (2) Pitch — does the tail have a hum or boom with a singable note to it (modal ringing), or is it pitchless? (3) Length — rank the room's tail from longest to shortest by the end of the tour; that ranking is your hands-on RT60 survey. Deliverable: a five-row journal table (room / flutter? / pitch? / tail rank / one-word character: "bathroom = bright cathedral, closet = dead in a good way"). After five rooms you'll be fluent — and your studio room's row stops being an opinion and becomes a measurement you made.

B2. The bass-null hunt, with a track you trust. ⭐⭐ (25 min) Pick one bass-heavy reference with strong sustained low end — widely used picks include James Blake's "Limit to Your Love" (the famous wobbling sub), Lorde's "Royals" (huge sub under a sparse arrangement), Billie Eilish's "bad guy," or Massive Attack's "Angel" — or any track from your Chapter 8 walk-test (its exercise B1 started this map; today you finish it). Loop the bassiest section at your marked level and hunt: corners first (expect bloom), then the walls, then a slow grid across the middle — crouching and standing at each stop, because modes have vertical maps too. Mark every spot where low notes swell absurdly and every spot where notes thin out or vanish — painter's tape on the floor makes the invisible visible. Then the verdict that matters: sit in your mixing chair and listen to one full bass line. Which notes drop? Which hang? Deliverable: your room's bass map (sketch with tape positions) plus a one-line chair verdict, written into the room's lies list. If a note vanishes at the chair, stand up while it loops — hearing it return as your head rises is the chapter's whole argument performed by your own skeleton.

B3. Hearing comb filtering on demand. ⭐⭐ (15 min) Three demonstrations, escalating. First: play steady noise-like sound (rain noise, pink noise, even a shower running) and slowly cup your palm a few inches from one ear, moving it closer and farther — that swooshing jet-engine color is a comb filter whose notches you're sliding by moving the reflector. Second: play pink noise or a dense mix through one speaker and walk slowly straight toward a bare wall, stopping with your head a foot from it; listen for the hollow, phasey shimmer as the wall's reflection sums with the direct sound at your ears. Third: in your DAW, put a flanger on a drum loop, set it slow and shallow — that's a comb filter set in deliberate motion. Deliverable: three journal lines describing the same signature in each ("hollow," "phasey," "swooshy" — your words), plus one sentence on where in your room you've heard this color uninvited. Once you can name it, you'll catch it at your mirror points before the mirror does.

B4. The before/after session. ⭐⭐ ★ (45 min, run twice: before and after your treatment pass) This is where the treatment pass proves itself — or gets caught loafing. Before you change anything: play your three Chapter 4 reference tracks at your Chapter 8 marked level from your exact mixing position. Full structured listening pass per track — low end, low-mids, mids, highs, then space, then width — journaling one line per zone, plus three specific observations you can re-test later ("bass note at 0:42 blooms and hangs," "hi-hats have an edge," "image vague around the snare"). After your treatment pass (any tier — even the $0 repositioning pass counts): same tracks, same marked level, same chair, same structured pass, without re-reading your before-notes first. Then compare the two entries. Deliverable: a dated before/after page in your journal listing what audibly changed, what didn't, and one surprise. Finish with the uncomfortable coda the chapter prescribed: play one of your own old mixes and log what the treated room reveals about the decisions your untreated room made for you. That last paragraph of notes is your personal tendencies list — Chapters 20–30 will cash it.

B5. Flutter kill, verified the honest way. ⭐ (10 min) Find your worst flutter pair from B1's studio-room row. Clap and listen three times to memorize the ring. Now hang a doubled moving blanket, duvet, or comforter over one of the two surfaces — change nothing else — and clap again from the same spot. Log the difference, then take the blanket down and clap once more to confirm the ring returns (single-variable discipline: you're proving the blanket did it, not your imagination). Deliverable: two journal lines and a decision — does that blanket earn a permanent hook on that wall?

B6. Modal ringing, note by note. ⭐⭐ (15 min) In your DAW, program a slow chromatic bass descent — half notes from C2 (about 65 Hz) down to E1 (about 41 Hz), each note cut dead by a short release, a beat of silence between. Play it through your monitors at the marked level, sitting in your chair with eyes closed. Two things to log: which notes hang on after their written ending (the room ringing — note the pitch and find its frequency from Appendix A), and which notes play noticeably quieter than their neighbors (your chair's nulls, now with note names). Deliverable: the descent annotated with "rings" / "vanishes" / "honest" per note. Keep it — exercise C4 will predict this list from a tape measure, and comparing prediction to ears is the day acoustics becomes yours.

Part C: 🎛️ DAW Lab

C1. Record the clap test. ⭐⭐ ★ (25 min) Ears first, evidence second — now get the evidence. Set up any mic you own (the pattern and model barely matter here) on a stand at your listening position, roughly ear height. Record yourself giving one sharp clap from beside the mic, then claps from your room's corners and your usual mic spot — a few seconds of silence around each. Now examine what the room printed: zoom into each clap's waveform and look at the tail — a clean room decays as a smooth fade; flutter shows up as a visible picket fence of evenly spaced repeats marching after the transient. Measure the spacing between two repeats (your DAW's selection-length readout, set to milliseconds) and check it against the round-trip distance between your flutter pair — sound covers roughly 1.13 feet per millisecond. Then loop just the ringy tail of your boomiest clap through a spectrum analyzer and find the frequency that's still standing while everything else dies. Deliverable: a screenshot or note of the flutter spacing and the ring frequency, filed in your session notes. Re-record the same claps after treating and keep both — there is no more satisfying before/after in this book.

C2. One source, three spots. ⭐⭐ (30 min) Record the same 20-second performance — your voice reading a verse, or an acoustic guitar part — in three locations: (1) the middle of your room, mic at mouth/instrument distance per Chapter 7; (2) a corner, facing into it; (3) your most-treated or softest spot (the blanket fort, the duvet corner, in front of your new panels). Same mic, same distance, same performance intensity; name the takes by location like an engineer (vox_center, vox_corner, vox_treated). Level-match them on playback — Chapter 4's discipline; an unmatched comparison is theater — and listen blind if you can recruit a second pair of ears. Deliverable: three journal verdicts in band vocabulary (where's the boxy 300 Hz honk? the flutter tail on consonants? the boom?) and a decision: which spot records your sources in your room, and what would make the runner-up usable?

C3. The walk-the-room bass hunt, formalized. ⭐⭐ (25 min) Turn exercise B2's hunt into a written protocol you can re-run after every change. In your DAW, build a test session: your bass-heavy reference on one track, and a test-tone generator on another (most DAWs ship one; otherwise import rendered sine files). Step one: the musical pass — B2's walk, logged. Step two: the surgical pass — play steady sine tones one at a time at moderate level (start with 50, 60, 80, 100, 120 Hz; add your C4-predicted mode frequencies once you have them) and for each tone, walk your room's center line front to back, then side to side at the chair, noting where each tone swells and where it nearly disappears. Mind your monitors' limits: small woofers at high level reproducing low sines is how tweeters' little brothers die — moderate level, short bursts. Deliverable: a per-frequency map ("60 Hz: dead at chair, huge at rear wall") filed with your session notes, plus the protocol itself written as a five-line checklist so future-you can repeat it identically after the next treatment tier.

C4. Compute your mode map. ⭐⭐ ★ (30 min) The sidebar's arithmetic, executed on your actual room — the chapter promised this walkthrough, and it pays off everything above. (1) Tape-measure your room's length, width, and ceiling height in feet (decimal feet: 10 feet 4 inches = 10.33). (2) For each dimension, compute f ≈ 565 ÷ L, then list that dimension's series: f, 2f, 3f, 4f — out to about 300 Hz. (3) Build the combined table, sorted by frequency, and flag trouble: any two modes within a few hertz of each other (stacking), and any wide gaps in the bass range (the broken-xylophone zones). (4) Map your chair: for each dimension, where does your listening position sit as a fraction of that dimension? Mark yourself against each mode's geography — mode 1 nulls at the halfway line, mode 2 at the quarter points — and predict which frequencies should dip and which should bloom at your seat. (5) Verify: play sine tones at your three lowest predicted problem frequencies and walk each one (per C3). Deliverable: the mode table with your chair's predictions, annotated with verdicts — predicted and confirmed, predicted and absent, surprise. Where prediction and ears agree, you now own the physics; where they disagree, remember the model only covers axial modes in a rectangular box — your bookshelf, doorway, and bed all vote too.

C5. The mirror-trick survey and the treatment plan. ⭐⭐ (30 min + build time if you're ready) Run the full mirror trick from your exact mixing position: both side walls (expect roughly two points per wall — one per speaker), the ceiling along the speaker-to-ear path, the wall behind the monitors, the desk itself (mirror flat on the desktop — can you see a tweeter?). Painter's tape on every hit. Photograph the taped room. Then produce the document this chapter has been building toward: your one-page treatment plan — every tape mark listed, the budget-table tier you're executing, the shopping list with estimated costs, and the install order (mirror points → flutter pair → worst corner → behind monitors → ceiling if anchorable). If you build this week: photograph after, re-run B4's after-session and C1's after-claps, and staple the whole packet — before photos, after photos, before/after journal, clap evidence — into your session notes. That packet is the cheapest upgrade documentation in audio, and a year from now it will be the proof of how far your ears have come.

C6. (Optional) Graphs after ears: the measurement-mic path. ⭐⭐ (60+ min, requires ~$100 measurement mic) If curiosity demands graphs: a calibrated measurement microphone plus Room EQ Wizard (free; Chapter 8's further reading pointed there) will sweep your room and draw what you've been hearing — the frequency response at your chair, peak by null, and the waterfall plot showing which frequencies ring longest in time. Measure at your listening position before and after treatment, overlay the two, and compare the graphs against your B2/B6/C4 findings. Deliverable: one paragraph on what the graphs confirmed, what they revealed that your ears missed, and what your ears caught that the single-position graph understates. Then put the mic away and go back to work — the chapter's order stands: ears first, graphs after, treatment above both.

Part D: Synthesis & Critical Thinking

D1. Choose the room, defend the choice. ⭐⭐⭐ ★ (25 min) You're moving, and two bedrooms are on offer for the studio. Room A: 11 × 13 feet, 8-foot ceiling, one window on a short wall, carpet. Room B: 10 × 10 feet, 9-foot ceiling, two big windows on adjacent walls, hardwood. Compute both rooms' first-mode series, assess stacking and gaps, then weigh the non-modal factors this chapter taught: window real estate versus panel real estate, floor reflection, where symmetry is achievable, tracking-versus-mixing duty. Write the memo: your pick, the three strongest acoustic reasons, the honest cost of what you gave up, and your first $100 of treatment in that specific room.

D2. The $250 allocation memo, for your actual room. ⭐⭐⭐** (30 min) Using your own diagnostics (B1, B2, C4, C5), write the one-page memo allocating a hypothetical $250 to your room — itemized, sequenced, and justified by your findings, not by the chapter's generic priorities. Renting with a no-holes lease? Solve for it (freestanding panels, tension rods, gobos, furniture redeployment) and note what the constraint costs you. Then the discipline test: identify the one purchase you most wanted to make that your diagnostics don't support, and write two sentences on why it waits. File the memo next to Chapter 8's honest-money memo; together they're your studio's constitution.

D3. The all-foam post-mortem. ⭐⭐⭐ (20 min) A friend proudly shows off a room checkered wall-to-wall with thin foam wedges — sixty of them, every surface, $300 all-in. Predict, in band vocabulary, exactly how this room sounds and why experienced ears call it worse than untreated: what happened to the treble, what didn't happen to the bass, and why mixes made there will translate badly in a specific direction (which way will their mixes lean, and where will it show up first?). Then write the rescue plan that keeps the sunk cost from compounding: what the existing foam can still honestly do, what gets bought next, and how you'd break the news without breaking the friendship — this chapter's no-gatekeeping clause applies to people, too.

D4. Argue against the chapter. ⭐⭐⭐ (25 min) Steelman the strongest honest case for skipping room treatment entirely: a reader who mixes exclusively on well-known headphones with a documented lies list (Chapter 8's method, done right), rents an apartment they'll leave within a year, and releases music that translates acceptably. Build their argument properly — headphones bypass the room; the lies list plus reference discipline catches most of what a treated room would; money and time are finite. Then locate precisely where the argument fails or narrows: what does every microphone they ever open still pass through, which Part III chapters does that implicate, and what's the minimum-viable concession (cost and hours) that covers the gap? End with a verdict: for this reader, what subset of the chapter is non-negotiable?

Part M: Mixed Practice

Interleaving earlier chapters — spaced retrieval is how this book sticks.

M1. (Ch 3 + Ch 8 + Ch 10) (15 min) Draw the complete monitoring chain from your DAW's master fader to your eardrum — every gain stage, every analog/digital boundary, in order — and extend it past the speaker cone the way this chapter insists. Annotate each stage with two things: whether it has a bypass, and which chapter taught you to trust it. Then mark where each of this chapter's three lies enters the chain, and write the one-sentence moral about why the final stage got a whole chapter to itself.

M2. (Ch 7 + Ch 10) (15 min) You're building the blanket fort for a vocal take with a cardioid mic. Using Chapter 7's polar-pattern logic, explain which direction the mic rejects, which wall's reflections it therefore hears loudest, and where the heaviest absorption goes as a result — then explain why the folk-remedy clothes closet often trades flutter for a boxy 300 Hz honk (which Chapter 4 band does clothing absorb, and which does it ignore?). Sketch the fort: singer, mic, fort walls, and the one wall you're allowed to neglect.

M3. (Ch 9 + Ch 10) (20 min) Open your Chapter 9 bass sketch — the MIDI part you programmed before you knew your room. Play it at your chair at the marked level and list every note you're tempted to "fix" (too loud, too long, too quiet). Now audition the same part from two other spots in the room (or on your headphones, lies list in hand) before touching anything. Deliverable: a two-column list — edits the part actually needs versus edits the room was dictating — plus one sentence on how Jaylen's A1 velocity discovery from the Project Checkpoint applies to your own session. Programming through a null writes the null into your bassline; this exercise is the antidote, run on your actual music.

M4. (Ch 1 + Ch 10) (10 min) Chapter 1's wavelength table predicted half of this chapter; prove you can run it yourself. Compute the approximate wavelength of 3 kHz (hi-hat sizzle territory) and of 60 Hz (808 territory) using speed of sound ≈ 1,130 feet per second. Using those two numbers, explain in three sentences why one folded moving blanket genuinely kills a flutter echo but does approximately nothing to a 60 Hz boom — and why the boom's fix lives in corners and cubic inches instead.

M5. (Ch 2 + Ch 4 + Ch 8 + Ch 10) (15 min) Your before/after session (B4) is an experiment, and experiments die by uncontrolled variables. List every variable the protocol deliberately holds constant — playback level (name the Chapter 4 perceptual law that makes this one non-negotiable), the reference tracks, the listening position, the files themselves — and then name two tempting mid-experiment changes that would quietly invalidate the comparison (a "small" monitor EQ tweak; new headphones; even fresh excitement, which is why the journal beats memory). Finish by explaining why sample rate and bit depth do not appear on the variables list, in one sentence that would make Chapter 2 proud.

Done? The quiz is next — closed book first pass, always. And if your room is still untreated as you read this sentence, the clap test takes ninety seconds and your hands are right there.